54 


MECHANICAL    DRAWING. 


To  fill  in  these  spaces,  draw  a  fairly  heavy  line  on  either 
side  of  the  space  to  be  filled ;  go  over  all  the  spaces  of  any  one 
portion  of  metal  and  allow  these  lines  to  become  dry ;  then 
open  the  pen  wider  and  fill  in  the  central  portions.  These 
filling  lines  are  drawn  with  the  R.  L.  pen  guided  by  the  tri- 
angle. Never  fill  in  with  a  writing-pen  or  use  the  R.  L.  pen 
as  a  brush. 

This  method  of  filling  the  spaces  causes  a  loss  of  time,  as 
the  first  lines  drawn  must  be  allowed  to  dry,  but  the  method 
is  a  safe  one.  A  more  rapid  method  and  a  better  one  after 
sufficient  experience  has  been  acquired  is  to  fill  each  of  the 
spaces  at  once  by  drawing  line  after  line  until  the  surface  of 
the  space  is  covered  with  liquid  ink.  The  ink  will  then  dry 
evenly  over  the  entire  surface  of  the  space.  Also,  this  allows 
of  continual  advancement  without  waiting  for  lines  to  dry. 
Caution  is  necessary  to  keep  the  triangle  well  away  from  the 
liquid  lines  of  ink  or  a  bad  blot  will  result. 

Just  as  good  ink-lines  are  required  for  hatching  as  for  the 
other  parts  of  the  drawing.  Do  not  attempt  to  make  the  lines 
of  hatching  too  fine. 

In  doing  hatching,  glance  back  after  drawing  every  ten  lines 


FIG.  37. 

or  so  to  see  that  the  spacing  continues  regular;  if  irregular, 
gradually  change  the  spacing  until  the  exact  amount  is 
obtained. 

In   drawing  sections  where   the  plane   passes   through  the 
center  line  of  a  cylindrical  body,  the   cylinder  is  generally  not 


GENERAL   DIRECTIONS. 


55 


hatched,  but  is  drawn  in  elevation,  resting  in  the  section. 
This  refers  to  shafts,  spindles,  bolts,  rivets,  etc.,  as  in  Fig.  37. 
Fig.  38  shows  a  Plan  and  Elevation  of  a  steam-cylinder. 
The  Plan  is  half  in  section,  the  section  taken  at  the  line  AB 
of  the  Elevation.  The  upper  half  of  the  half-cylinder  is 
removed  and  the  section  drawn,  the  lower  flange  of  the 

i 


FIG.  38. 

cylinder  showing  below  the  section.  Each  bolt-hole  is  drawn, 
and  the  centers  marked,  first  by  the  circular  center  line  and 
also  by  the  short  radial  lines. 

The  elevation  of  the  cylinder  is  also  half  in  section,  the 
section  made  at  the  plane  CD  in  the  Plan.  In  this  case  the 
front  half  of  the  half-cylinder  is  removed  and  the  section 
drawn.  The  top  and  bottom  lines  of  the  flanges  and  the 
opening  at  the  bottom  are  carried  across  to  the  center  line. 
The  lower  line  of  the  upper  flange  in  the  section  is  a  broken 
line,  as  this  rim  of  the  flange  is  concealed  behind  the  section. 


:i 


MECHANICAL  DRAWING. 


WRITTEN    FOR     THE     USE     OF     THE     MIDSHIPMEN 
AT   THE   UNITED    STATES    NAVAL   ACADEMY. 


BY 


F.    W.    BARTLETT, 

Captain,  U.  S.  Navy 


THIRD    EDITION,  REVISED 
FIRST   THOUSAND 


NEW  YORK: 
JOHN   WILEY   &   SONS. 

LONDON:    CHAPMAN  &   HALL,   LIMITED. 
1911. 


Copyright,  1901,  1911, 

BY 
F.  W.   BARTLETT, 


THE  SCIENTIFIC   PRESS 

ROBERT   DRUMMOND  AND   COMPANY 

BROOKLYN,    N.   Y. 


PREFACE  FOR   THIRD  REVISED  EDITION. 


THIS  text-book  has  been  in  use  for  ten  years  at  the  United 
States  Naval  Academy,  and  the  course  in  Mechanical  Drawing 
has  been  very  successful. 

From  the  experience  of  these  years  the  book  is  revised  and  the 
lately  adopted  methods  of  the  Navy  Department  have  been 
incorporated.  The  changes  are  particularly  in  regard  to  the 
adoption  of  Standard  Lines  for  the  different  Bureaux.  In  addi- 
tion the  first  two  sheets  have  been  combined  in  one,  to  reduce 
the  time  devoted  to  technique. 

F.  W.  BARTLETT, 

March,  1911.  Captain,    U.  S.   Navy. 

iii 


241310 


PREFACE. 


THE  attempt  is  made  in  this  treatise  to  find  the  methods 
of  practical  work  in  use  in  most  drafting-rooms  and  to  give 
these  methods  in  detail  for  the  use  of  those  studying  Mechan- 
ical Drawing. 

The  author  has  endeavored  to  eliminate  any  personal 
peculiarity  of  method,  and  has  based  the  treatise  on  the 
methods  in  use  in  the  United  States  Navy,  as  far  as  these 
methods  could  be  determined.  As  general  methods  differ 
slightly,  the  drawings  referred  to  for  the  general  instruction 
have  been  those  of  the  Bureau  of  Steam  Engineering  of  the 
Navy  Department,  and  the  methods  of  that  bureau  have 
been  followed.  The  special  methods  of  the  Bureau  of  Ord- 
nance and  of  the  Bureau  of  Construction  are  studied  and 
used  after  the  main  course  is  completed.  The  differences 
are,  however,  slight  and  refer  principally  to  center  lines 
and  dimension  lines.  The  Bureau  of  Ordnance  uses  the 
decimal  scale  also. 

All  the  minor  points  of  method  that  are  found  only  by 
experience  cannot  be  given  to  a  large  class  by  a  small  corps 
of  instructors,  and  the  endeavor  is  made  to  place  these 
methods  where  they  may  be  found  and  studied.  The  in- 
structor may  then  refer  each  one  to  the  book  instead  of 
giving  to  each  individual  the  same  detail. 


VI  PREFACE. 

The  system  of  instruction  urged  does  away  with  copying. 
In  fact,  no  copying  is  allowed  and  no  drawings  are  available 
for  copying. 

The  First  Drawing  is  purposely  full  of  detail,  so  that 
the  eye,  mind,  and  hand  may  be  trained  to  accuracy  together, 
each  depending  on  the  others.  The  instruction  lessens  as 
the  figures  follow  each  other,  only  the  new  and  most  impor- 
tant points  being  noticed.  The  attempt  is  made  to  have 
the  triangular  scale  used  so  that  it  will  be  thoroughly 
understood. 

No  Geometry  or  Descriptive  Geometry  is  given,  as 
these  branches  are  taught  in  the  department  by  another  text- 
book. 

All  but  Sheet  II  has  been  carefully  criticised  by  Mr. 
A.  M.  P.  Maschmeyer,  Chief  Draftsman  in  the  Bureau  of 
Steam  Engineering  at  the  Navy  Department,  and  the  author 
is  much  indebted  to  him  for  his  kindness  and  his  thorough 
criticism. 

The  naval  officers  associated  in  this  work  have  assisted 
materially  with  suggestions.  I  am  particularly  indebted  to 
Lieut.  Commander  John  L.  Gow,  U.  S.  Navy,  for  his  un- 
sparing and  accurate  criticisms. 

F.    W.    BARTLETT, 

Lieut.  Commander,  U.  S.  N. 

(1901) 


CONTENTS. 


PAGE 

THE  DRAWING  COURSE xi 

USE  OF  INSTRUMENTS i 

Drawing-board i 

Thumb-tacks 2 

Pencils  and  Pencilling 2 

Sharpening  the  lead 3 

Ink 5 

Red  Ink 6 

T  Square 6 

Triangles 8 

To  Test  Triangles '. 9 

The  Triangular  Scale 10 

To  Use  the  Scale 13 

Triangular-scale  Guard 13 

Right-line  Pen 13 

Use  of  the  R.  L.  Pen 14 

To  Examine  and  Test  the  R.  L.  Pen 18 

To  Sharpen  the  R.  L.  Pen 18 

Compasses 19 

To  Test  the  Compasses 20 

To  Use  the  Compasses 20 

Extension-bar 21 

Bow  Spacers 22 

Bow  Pencil  and  Bow  Pen 23 

Dividers 24 

To  Use  the  Dividers 24 

Irregular  Curves 25 

Protractors 26 

To  Use  the  Protractors 26 

Erasers 27 

Erasing  Shields 28 

Horn  Center 28 

Brushes 29 

Pricker 29 

Beam-compasses  or  Trams 20 

vii 


V1U  CONTENTS. 

PAGE 

Foot  Rule 30 

Calipers. 30 

Splines 31 

Lead-wire 31 

Paper-cutters 31 

GENERAL  DIRECTIONS 32 

Stretching  Paper 32 

Profile  Drawings 34 

General  Arrangement 34 

Working  Drawings 35 

Views 36 

Projections 38 

Lines 40 

Center  Lines 41 

Shade  Lines 43 

Shafts  and  Other  Cylindrical  Objects , 49 

Sections 50 

Hatching 51 

Breaks 56 

Dimension  Lines;  Dimension  Extension  Lines 57 

Threads 62 

Square  Threads 67 

Bolts  and  Nuts 70 

Jam-nuts 74 

Tails 74 

Working,  Border,  and  Cutting  Lines 75 

Legend,  Lettering,  Scale,  etc 76 

Block  Letters 79 

Free-hand  Lettering 83 

Scales 83 

Line  Shading  and  Tinting 84 

Flat  Surfaces 84 

Cylinder 85 

Interior  of  Hollow  Cylinder 88 

Cone 88 

Sphere 90 

Tinting 91 

To  Prepare  the  Tint 91 

To  Lay  on  a  Flat  Tint 92 

Tinting,  Cylinder 94 

Cone 94,  95 

Sphere 95 

Stippling 96 

Tracing 96 


CONTENTS.  IX 

PAGE 

Blue-printing 97 

Sketches 98 

Plan  of  Procedure  in  Making  a  Drawing 101 

Pencilling  the  Drawings io2 

Plan  of  Procedure  in  Inking 103 

General  Remarks 104 

FIRST  DRAWINGS 106 

General  View  of  Sheet  1 106 

Sheet  I.  Straight  and  Curved  Lines 107 

Fig.  A.  Horizontal  Full  and  Broken  Lines 109 

B.  Vertical  Heavy  Lines no 

C.  45°  Triangle 112 

D.  45°  Triangle 113 

E.  60°  Triangle 114 

F.  45°  Triangle 115 

G.  45°  and  60°  Triangles 1 16 

H.  60°  Triangle 117 

I.  Bow  Spacers 118 

J.  Section  Hatching 119 

K.  Compass 121 

L.  Compasses,  Bow,  Pencil  and  Pen 122 

M.  Bow,  Pencil  and  Pen 123 

N.  Fillets 124 

O.  Two  Arcs 126 

P.  Protractor,  Arcs  and  Straight  Lines 127 

Q.  Tangent  Arcs 128 

R.  Connecting  Arcs 129 

S.  Ellipses;  Irregular  Curves 131 

T.  Heavy  'Lines,  Spaces  between 133 

U.  Shading  Circles;  Hatching 134 

Legend 135 

Complete  Drawing,  Sheet  1 136,  137 

Sheet  II.  Working  Drawings 137 

Description  of  Models 137 

General  Description  of  Sketching 138 

General  Directions  for  Drawing  Sheet  II 141 

Positions  of  the  Views 142 

Model  1 143 

Sketching 143 

Dimensions 145 

Sections 147 

Directions  for  Drawing 148 

Model  II 149 

Sketching 149 


X  CONTENTS. 

PAGE 

Sections 150-152 

Dimensions 152 

Directions  for  Drawing 153 

Model  III 154 

Sketching 154 

Sections 155,  157 

Dimensions 156 

Directions  for  Drawing 157 

Legend 159 

STANDARD  DIMENSIONS  OF  BOLTS  AND  NUTS  FOR  THE  UNITED  STATES  NAVY.  160 

STANDARD  HATCHING 161 

LINES  TO  BE  USED  ON  DRAWINGS 162 

INDEX 163 


THE   DRAWING   COURSE. 


IT  is  considered  that  the  most  important  parts  of  the 
course  are : 

First.  Instruction  in  the  use  of  the  instruments;  in  mak- 
ing clean,  sharp  lines;  in  connecting  lines  cleanly  together; 
the  technique  generally. 

Second.  Instruction  in  quickly  and  accurately  making  a 
correct,  dimensioned  sketch  of  any  piece  of  mechanism ;  and 
from  the  sketch  making  a  working  drawing  so  that  the 
mechanism  may  be  reproduced  with  certainty. 

Third.  Instruction  in  carefully  and  accurately  making 
tracings  and  blue-prints  from  either  the  inked  or  pencilled 
working  drawings. 

Fourth.  Instruction  in  quickly  and  accurately  reading 
drawings. 

Fifth.  Special  instruction  in  engineering,  ordnance,  and 
ship-building  methods. 

It  is  found  by  experience  that  the  second  and  fourth  parts 
of  the  course  are  much  more  important^  than  the  others  and 
the  instruction  tends  towards  developing  these  two  at  the 
expense  of  the  time  previously  allotted  to  the  others. 


MECHANICAL    DRAWING. 


USE    OF    INSTRUMENTS. 

Drawing-board. — One  edge  only  of  the  drawing-board  is 
made  a  true  plane.  The  accuracy  of  the  drawings  depends  on 
this  plane  being  true.  This  is  the  ''working-edge"  and  is 
marked  by  a  circular  stamp  along  the  middle  of  the  upper  face 
of  the  board.  When  in  use,  this  "working-edge"  is  at  the 
left,  the  stamped  face  upwards. 

The  "working-edge  "  of  the  board  is  considered  for  con- 
venience as  the  W.  side  of  the  board,  so  that  the  side  away 
from  the  position  of  the  draftsman  is  the  N.  side  of  the  board, 
etc. 

The  lines  from  E.  to  W.  on  the  board  are  considered  hori- 
zontal lines;  those  from  N.  to  S.  vertical  lines. 

When  beginning  a  new  drawing,  take  the  drawing-board 
and  T  square  to  the  pattern-maker  to  have  them  ' '  trued  up  "  ; 
in  other  words,  to  make  the  "working-edge"  of  the  board 
and  the  sliding-edge  of  the  T  square  true  planes.  At  the 
same  time  the  T  square  is  tested  to  make  sure  that  the  top 
edge  of  the  blade  is  at  right  angles  to  the  sliding-face  of  the 
head. 


2  MECHANICAL   DRAWING. 

The  drawing-board  is  to  be  kept  horizontal  or  very  slightly 
inclined  at  the  height  desired,  the  work  done  standing. 

When  first  beginning  work,  swing  the  board  around  until 
the  best  light  is  obtained,  the  direction  of  the  light  to  be  from 
the  left-hand  top  (N.  W.)  corner.  Test  this  by  placing  the 
T  square  and  triangle  in  position  and  noting  if  the  edges  to  be 
drawn  by  are  in  light  or  shadow.  While  drawing,  test  often 
for  light,  as  the  work  will  be  poor  if  the  light  is  bad  and  the 
eyes  will  suffer. 

Thumb-tacks. — These  are  used  in  securing  drawing-  and 
tracing-paper  on  the  boards.  When  first  inserted  in  the  paper 
the  heads  may  be  tipped  at  an  angle  towards  the  center  of  the 
paper,  so  that  when  straightened  up  in  pushing  them  into  the 
wood  they  may  slightly  assist  in  stretching  the  paper. 

They  are  always  pushed  down  firmly  when  used. 

To  secure  paper  or  tracing-cloth  on  the  boards. — Place  the 
paper  in  position  as  desired;  put  in  a  thumb-tack  at  the 
middle  of  the  top  line  of  the  paper;  slide  the  hand  with 
a  gentle,  firm  pressure  from  this  tack  down  to  the  middle  of 
the  bottom  line  of  the  paper  and,  while  firmly  holding  the 
paper  as  stretched,  insert  another  thumb-tack;  begin  at  the 
center  of  the  board  and  slide  the  hand  to  the  right  with  the 
same  pressure  and  insert  a  tack  at  the  middle  point  of  the 
right-hand  line  of  the  paper;  do  the  same  to  the  left;  begin 
again  at  the  middle  of  the  board  and  slide  the  hand  with  the 
same  pressure  towards  a  corner  and  insert  a  tack;  repeat  for 
the  other  corners.  In  each  case,  be  sure  to  keep  the  pressure 
until  the  tack  is  fast.  It  may  be  necessary  to  insert  tacks 
between  those  already  placed.  In  each  case  press  the  paper 
as  described. 

Pencils  and  Pencilling. — The  pencil-work  of  a  drawing  is 
most  important.  Good  ink-work  never  hides  defects  of  bad 
pencil-work.  The  accuracy  of  the  drawing  depends  almost 
entirely  on  good  pencil-work. 

Make  clean,  sharp  lines — not  faint  ones;  it  is  difficult  in 


USE    OF  INSTRUMENTS.  3 

inking  or  tracing  a  drawing  to  find  the  faint  lines,  and  the  eyes 
are  strained  by  the  close  vision  required.  Even  though  slight 
depressions  are  made  in  the  paper  by  making  firm  lines,  it  is 
best  to  do  this  and  save  the  eyes. 

Draw  all  pencil-lines  full  and  broken  as  required.      It  is  a 

waste  of  time  to  begin  and  stop  the  pencil-lines  at  the  exact 

points  where  the  ink-lines  will  begin  and  end.      Sweep  through 

*the  terminal  points  of  the  line,  but  no  farther  than  necessary. 

Pencil-lines  are  easily  erased  after  the  inking  is  completed. 

The  leads  in  the  pencils  used  should  be  HHHHHH  or 
HHHHHHH.  These  marks  are  found  on  the  pencil  or  on 
the  box  of  leads  used  with  the  artist's  pencil. 

Never  use  a  soft  lead  for  any  purpose  on  a  drawing-board. 

Sharpen  the  pencil-points  frequently 

The  best  point  for  the  pencil  is  the  long  chisel-point 
narrowed  to  about  one-third  the  thickness  of  the  lead. 

Fig.  I  shows  the  proper  sharpening  of  the  lead-pencil  The 
longer  bevels  are  from  2"  to  3"  long,  and  the  shorter  ones  from 
\\"  to  2"  long,  axially. 

Fig.  2  shows  the  proper  method  of  sharpening  the  lead  for 
the  artist's  pencil.  The  length  of  the  longer  bevel  along  the 
axis  of  the  lead  is  from  f "  to  £". 

It  is  even  advisable  to  make  the  point  thinner  as  in  Fig.  3, 
but  there  is  more  danger  of  breaking  the  lead  through  care- 
lessness. For  the  compasses  and  bow  pencil,  narrow  the  flat 
edge  still  more  and  take  care  to  place  the  flat  edge  of  the 
pencil-point  so  that  it  is  tangent  to  the  arc  drawn. 

Another  good  point  is  made  by  sharpening  the  lead  with 
a  cut  clear  across  at  .an  angle,  as  shown  in  Fig.  4.  This 
method  is  by  many  considered  best,  as  the  outer  skin  of  the  lead 
is  hardest  and  wears  better.  Also,  less  time  is  required  for 
sharpening,  and  the  point  is  rounded.  It  is  considered 
especially  good  for  compasses  and  bow  pencils. 

Sharpening  the  Lead. — If  a  file  is  used,  the  lead  is  sharp- 
ened by  rubbing  it  along  the  rougher  side  of  the  file  until  it  is 


ME  CHA  NIC  A  L   DRA  WING. 


shaped  and  then  finishing-  on   the  smoother  side   of  the  file. 
Support  the  end  of  the  file  when  sharpening  the  lead. 

In  the  last  sharpening,  roll  the  lead  a  little  on  the  file  so 


as  to  round  the  corners  slightly.  Finally,  rub  the  flat  edges 
on  a  piece  of  drawing-paper,  rolling  as  before ;  this  will  remove 
the  rough  edges  left  by  the  file. 


USE   OF  INSTRUMENTS.  5 

As  files  soon  wear  out,  many  prefer  pads  made  of  strips  of 
sandpaper. 

It  is  a  good  practice  to  have  one  end  of  the  pencil  sharp- 
ened with  a  chisel-edge  and  one  with  a  round  (needle)  point 
for  marking  dimensions,  both  leads  hard ;  but  it  is  better  for 
very  accurate  work  to  mark  off  dimensions  with  the  sharp 
points  of  the  dividers  or  bow  spacers ;  or,  better  still,  if  such 
an  article  is  at  hand,  the  pricker. 

In  using  the  pencil,  keep  it  nearly  vertical  and  keep  the 
arm  away  from  the  body.  Do  not  hold  the  pencil  so  that  the 
point  is  in  the  angle  between  the  guiding-edge  and  the  paper: 
keep  it  vertical. 

Use  the  pencil  with  a  free  sweep,  keeping  the  eye  along 
the  line  of  the  T  square  or  triangle  if  possible. 

Always  draw  from  left  to  right,  and  always  away  from  the 
body. 

Considerable  practice  will  be  required  in  order  to  draw  a 
line  accurately  through  two  points  when  the  pencil  is  guided 
either  with  the  T  square  or  the  triangle.  In  the  case  of  the 
triangle,  for  instance,  if  the  two  points  are  marked  and  it  is 
desired  to  draw  a  line  through  the  middle  of  each  mark,  place 
the  triangle  very  near  the  points  but  not  exactly  up  to  them, 
as  the  pencil  must  be  held  vertical  and  not  bent  over  to  fit 
sharply  into  the  angle  between  the  triangle  and  the  paper. 
Hold  the  pencil  properly  and  draw  a  short  line  through  the 
left-hand  point ;  if  it  is  not  in  the  center  of  the  mark,  the  tri- 
angle must  be  moved  a  little  and  the  attempt  repeated.  After 
the  line  is  correct,  carry  the  hand  along  in  the  same  position 
to  the  other  point  and  again  test  by  a  short  line.  When  the 
two  short  lines  agree  with  the  centers  of  the  two  marks,  return 
to  the  left  and  sweep  the  line  across,  carefully  holding  the 
hand  in  the  same  position  and  resting  the  last  two  fingers  on 
the  triangle. 

Ink. — The  best  drawings  can  be  made  only  by  using  the 
best  Indian  or  Chinese  ink.  This  consists  of  carbon  mixed  with 


O  MECHANICAL   DRAWING. 

some  adhesive  substance,  and  lies  wholly  on  the  surface  when 
used  on  the  drawing-board,  and  can  be  readily  erased  if  neces- 
sary. It  is  furnished  in  blocks  of  varying  sizes,  and  is  ground 
in  water  in  any  convenient  receptacle.  Special  forms  of  ink- 
saucers  are  made  with  glass  covers  to  reduce  evaporation  and 
keep  out  dust. 

As  considerable  time  is  required  to  mix  the  ink,  and  as  ink 
must  be  freshly  mixed  to  be  good,  it  is  often  necessary  to  use 
one  of  the  kinds  of  permanently  mixed  inks  furnished  in 
bottles.  The  results  are  not  as  good  as  can  be  obtained  with 
the  stick  ink,  but  the  time  required  for  mixing  the  ink  cannot 
always  be  spared. 

Red  Ink. — This  is  now  seldom  or  never  used.  It  flows 
more  freely  than  the  Indian  ink,  and  greater  care  must  be 
observed  in  its  use,  as  it  is  much  more  likely  to  run  out  of  the 
pens  against  the  triangles  and  T  squares.  The  outside  of  the 
pen  must  be  carefully  wiped  after  the  pen  is  rilled;  the  pen 
must  not  be  rilled  as  full  as  with  the  black  ink ;  and  care  must 
be  taken  not  to  hold  the  pen  too  near  the  triangles  or  T  square 
when  making  lines. 

Whenever  occasionally  red  ink  is  used,  all  red-ink  lines 
are  fine  lines. 

T  Square. — On  the  working-edge  of  the  drawing-board 
and  on  the  T  square  depend  primarily  the  accuracy  of  the 
drawings. 

The  T  square  consists  of  the  head  and  the  blade.  Some- 
times they  are  fixed  at  right  angles  to  each  other;  and  some- 
times the  blade  is  movable  and  may  be  clamped  at  any  desired 
angle  with  the  head.  The  fixed  blade  answers  all  practical 
purposes  for  general  work. 

The  sliding-edge  of  the  head  of  the  T  square  is  made  a 
true  plane,  and  this  edge  slides  along  the  "  working-edge  "  of 
the  drawing-board,  so  that  all  lines  drawn  along  the  blade  in 
the  various  positions  of  the  head  will  be  parallel.  In  the 
fixed -blade  type,  the  top  of  the  blade  is  accurately  planed  so 


USE   OF  INSTRUMENTS.  ? 

as  to  be  at  right  angles  to  the  head,  so  that  all  lines  drawn 
along  this  top  of  the  T  square  will  be  at  right  angles  to  the 
"working-edge"  of  the  board.  Since  the  triangles  are 
accurately  squared,  the  vertical  lines  drawn  when  the  triangle 
rests  on  the  T  square  in  position  will  be  parallel  to  the 
"  working-edge  "  of  the  board. 

Lines  should  of  course  be  drawn  with  the  upper  edge  of 
the  T  square  only  as  a  guide. 

The  T  square  is  used  for  all  horizontal  lines.  It  cannot 
be  depended  upon  for  the  vertical  lines,  as  the  bottom  of  the 
board  is  not  planed  at  right  angles  to  the  "working-edge." 

It  is  held  with  the  head  firmly  pressed  against  the  ' '  work- 
ing-edge "  by  the  left  hand,  and  is  moved  along  that  edge  by 
the  left  hand.  It  must  never  be  moved  with  the  right  hand 
on  the  blade  or  with  both  hands  pushing  the  blade,  or  with  the 
right  hand  assisting  the  left  by  pushing  on  the  blade  at  the 
same  time  as  the  left  hand  moves  the  T  square. 

Stretch  the  first  finger  and  the  wrist  of  the  left  hand  along 
the  head  of  the  T  square  equally  on  both  sides  of  the  blade, 
making  the  support  as  long  as  possible. 

The  vertical  lines  are  drawn  by  using  the  triangles  as 
guides.  These  are  moved  along  the  T-square  as  it  is  firmly 
held  in  position  with  the  left  hand.  As  both  hands  are 
required  in  using  the  triangles  in  this  manner,  after  the  triangle 
is  nearly  in  the  proper  position,  slide  the  left  hand  along  the 
blade  of  the  T  square,  always  pressing  to  the  right  and  down- 
ward, and  hold  the  T  square  with  some  of  the  fingers  and 
move  the  triangle  along  with  the  others.  Often  test  the  posi- 
tion of  the  T  square  by  moving  the  left  hand  back  to  the  head 
of  the  instrument,  again  sliding  it  along  the  blade  as  before. 

Never  guide  a  knife  in  cutting  paper  with  the  upper  edge 
of  the  T  square.  Use  the  lower  edge;  or,  Ibetter  still,  use  the 
knife  with  no  guide  but  the  eye  and  the  line  drawn  for  cutting. 

Use  no  weights  to  hold  the  T  square  or  triangles  in  posi- 
tion. 


8  MECHANICAL    DRAWING. 

Triangles. — The  triangles  are  45°  and  60°.  The  45°  tri- 
angle has  equal  angles  at  the  ends.  The  60°  triangle  has  one 
60°  and  one  30°  angle.  The  other  angles  of  both  triangles 
are  right  angles  and  are  very  accurately  constructed.  In  the 
case  of  the  45°  triangle,  the  two  shortest  sides  are  equal  in 
length ;  in  the  60°  triangle,  the  shortest  side  is  half  the  length 
of  the  longest. 

The  triangles  rest  against  the  T  square  and  are  used  in 
drawing  the  vertical  lines  of  the  drawings.  These  lines  are 
then  parallel  to  the  "working-edge"  of  the  drawing-board. 
In  drawing  these  vertical  lines  always  place  the  triangle  on  the 
T  square  so  that  the  left  side  of  the  triangle  will  be  the  one  ver- 
tical. In  this  manner  the  light  will  always  come  from  the  left. 

To  Draw  Parallel  Lines  with  the  Triangles. — After  one  line 
is  drawn  with  a  triangle,  to  draw  others  parallel  to  it,  place 
the  triangle  near  the  line  and  parallel  to  it,  as  if  the  line 
were  to  be  drawn  again.  Do  not  attempt  to  place  the  triangle 
edge  exactly  on  the  line,  as  it  will  be  found  very  difficult  to 
get  it  exactly  right,  whereas  it  may  be  readily  brought  near 
and  parallel.  Hold  this  triangle  firmly  and  bring  the  other 
triangle  against  one  edge  of  it;  then  hold  the  second  one 
firmly  and  move  the  first  one  along  the  edge  of  the  fixed 
one  until  the  desired  point  is  reached,  when  the  line  may  be 
drawn.  This  may  be  repeated  for  a  number  of  lines  parallel 
to  the  first  one  drawn.  The  left  hand  must  hold  both  triangles 
when  the  lines  are  drawn,  some  of  the  fingers  on  each; 
generally  the  thumb  and  last  two  fingers  hold  the  fixed  tri- 
angle, and  the  first  and  middle  fingers  move  along  and  secure 
the  one  moved. 

Angles  of  15°,  30°,  45°,  60°,  75°,  and  90°  may  be  drawn 
by  the  combination  of  the  T  square  and  the  two  triangles. 

Never  construct  angles  by  drawing  lines  along  adjacent 
sides  leading  from  a  vertex.  It  is  even  well  to  cut  about  J" 
from  all  the  corners  of  the  triangles,  as  these  corners  are  often 
bent  and  unreliable. 


USE   OF  INSTRUMENTS.  9 

In  drawing  lines  with  the  triangles  as  guides,  always 
arrange  so  that  the  hand  holding  the  R.  L.  pen  rests  on  the 
triangle. 

To  Test  Triangles. — For  the  straightness  of  the  edges, 
an  accurate  steel  straight-edge  is  generally  a  sufficient  test; 
but  if  great  care  is  required,  the  following  method  may  be 
used :  Push  a  very  fine  needle  vertically  into  the  paper ;  at  a 
distance  just  less  than  the  length  of  the  edge  to  be  tested,  push 
another  needle  of  the  same  kind  into  the  paper  vertically. 
Place  the  edge  to  be  tested  against  the  needles  and  draw  a  fine 
line,  holding  the  pencil  with  great  care  and  always  in  the  same 
position  relatively  to  the  edge.  Place  the  edge  on  the  other 
side  of  the  needles  and  drawn  another  line.  The  errors  are 
doubled. 

To  Test  the  Right  Angle. — Place  the  triangle  on  the  T 
square  and  draw  a  vertical  line  through  a  point  chosen.  Re- 
verse the  position  and  draw  another  line  through  the  same 
point.  The  error  is  doubled. 

To  Test  the  4.5°  Angle. — Fig.  5.  Draw  accurately  a  large 
circle.  Lay  the  45°  triangle  in  position  on  the  T  square  and 


draw  lines  through  the   center  as  shown.      Test  with  the  T 
square  the  horizontal  accuracy  of  the  intersections  a  and  b,  c 
and  d.     An  additional  test  may  be  made  by  spacing  off  ab  with 
the  dividers  and  comparing  the  length  with  bd,  dc,  and  ca. 
To  Test  the  60°  Angle. — Fig.  6.      Draw  accurately  a  large 


IO  MECHANICAL  DRAWING. 

circle.  Draw  the  horizontal  center  line.  With  the  60°  triangle 
in  position  on  the  T  square,  draw  the  60°  lines  as  shown.  Test 
with  the  T  square  the  horizontal  accuracy  of  the  intersections  b 
and  £,/and  e.  Space  be  and  compare  with  cd,  de,  ef,  fa  and  ab. 

To  Test  the  jo°  Angle. — Use  the  above  method,  drawing 
also  the  vertical  center  line. 

The  Triangular  Scale. — The  triangular  scale  is  used  for 
all  measurements  on  the  drawing-board,  and  is  an  instrument 
of  great  accuracy  and  should  be  carefully  treated. 

This  scale  should  never  be  used  except  on  the  drawing- 
board. 

It  should  never  be  used  for  measuring  any  piece  of 
mechanism,  as  it  would  soon  have  its  edges  battered  and  would 
be  useless  for  accurate  work.  Lines  should  never  be  drawn 
along  its  edge;  in  other  words,  it  should  never  be  used  as  a 
ruler. 

Distances  should  never  be  taken  from  it  by  compasses  or 
dividers,  as  the  points  of  these  would  ruin  the  scales ;  besides, 
this  method  of  measuring  is  not  as  accurate  as  that  of  using  the 
scale  properly. 

There  are  ten  different  scales  on  the  rule  furnished,  so  that 
drawings  may  be  made  from  ' '  full  size  "  to  -^  size  by  using 
the  different  scales. 

Small  figures  on  the  right  or  left  indicate  the  scales. 

The  principal  scale  is  marked  32  and  is  the  only  one  on 
that  flat  of  the  rule.  This  is  the  "  full  size  "  scale  where  the 
foot  is  divided  into  inches  and  the  inches  into  halves,  quarters, 
eighths,  sixteenths,  and  thirty-seconds;  hence  the  32  scale. 

As  most  small  measurements  in  engineering  practice  are 
given  in  these  fractions  of  an  inch,  this  scale  is  the  common 
one — being  like  the  ordinary  one-foot  or  two-foot  rule. 

Another  scale,  marked  10,  is  also  the  only  one  on  its  flat 
of  the  rule,  the  foot  being  subdivided  into  inches  and  the  inches 
into  tenths.  This  scale  is  used  in  ordnance  work  in  the  U.  S. 
Navy. 


USE   OF  INSTRUMENTS.  II 

The  other  scales  are  for  the  purpose  of  making  drawings  of 
reduced  sizes.  The  figures  to  the  right  or  left  indicate  what 
number  of  inches  or  what  portion  of  an  inch  represent  one  foot. 
Thus,  to  make  a  drawing  of  ''one-fourth  size"  or  "  one- 
quarter  size,"  instead  of  using  the  32  scale  and  mentally  cal- 
culating each  dimension  in  order  to  draw  it  one-fourth  its 
actual  size,  use  the  scale  marked  3.  This  means  that 
3"  =  i  foot,  or  that  a  distance  of  3"  is  used  to  represent  a  foot 
of  length  and  is  divided  up  into  twelve  parts,  each  representing 
one  inch.  These  representative  inches  are  again  divided  into 
halves,  quarters,  and  eighths.  Then,  instead  of  calculating  a 
distance,  it  is  taken  directly  from  this  scale,  the  calculation 
already  made,  so  that  the  distance  marked  off  will  be  exactly 
one-fourth  of  the  true  distance. 

The  other  scales  are  for  the  same  purpose  for  different  frac- 
tions of  full  size. 

Mark.  Size.  Stated  on  Drawings. 

32  Full  size  Scale,  full  size 

10  Full  size  Scale,  full  size,  decimal 

4  One-third  Scale,  4"    =  i  foot 

3  One-fourth  Scale,  3"    =  i  foot 

2  One-sixth  Scale,  2"    =  i  foot 

ij  One-eighth  Scale,  i£"  =  i  foot 

i  One-twelfth  Scale,  i"    =  i  foot 

f  One-sixteenth  Scale,  J"    =  i  foot 

•J-  One-twenty-fourth  Scale,  \"    =  i  foot 

f  One-thirty-second  Scale,  f"    =  i  foot. 

Of  course,  as  the  fraction  of  full  size  is  reduced,  the  number 
of  divisions  on  the  representative  foot  is  lessened ;  for  instance, 
on  the  scale  of  f "  =  I  foot  the  smallest  division  of  the  three- 
eighths  inch  represents  one  inch  of  the  full  size,  and  the  inches 
are  not  marked  with  figures. 

For  all  except  the  32  and  10  scales  there  are  two  scales 
on  the  same  flat,  so  that  either  may  be  used.  As  one  of  these 


12  MECHANICAL   DRAWING. 

scales  is  always  equal  to  twice  the  other,  there  is  no  difficulty 
in  taking  off  any  dimension. 

For  distances  over  one  foot  the  scales  are  marked  for  feet, 
beginning  from  the  o  mark.  For  instance,  using  the  scale  of 
\\"  =  I  foot,  the  o  mark  is  towards  the  center  of  the  rule, 
and,  looking  towards  the  right,  we  find  along  the  same  line  on 
which  the  o  is  placed  a  figure  2.  This  is  2  feet.  Farther  on 
is  a  figure  4  for  4  feet.  The  unmarked  lines  between  o  and 

2  and  2  and  4  are  I  foot  and  3  feet  respectively. 

Note  that  the  inches  and  feet  are  always  on  the  same  line 
as  the  o  mark. 

If  using  the  scale  at  the  other  end  of  the  same  flat,  the 
3"  =  i  foot  scale,  we  find  that  the  o  mark  is  below  the  flat 
surface  and  on  the  curved  portion.  Then,  for  using  this  scale 
for  distances  of  over  one  foot,  we  must  look  along  the  line 
where  the  o  is  placed  or  in  the  curved  portion.  Here  we  find 
I  and  2. only.  In  order  then  to  measure  2  ft.  7-f",  we  place 
the  2  mark  at  the  starting-point  and  follow  along  to  o  and 
then  find  7"  and  then  the  f ". 

To  measure  3  ft.  7f7/  on  the  scale  of  \\"  —  I  foot,  we 
look  along  the  flat  portion  in  line  with  the  o  for  that  scale  and 
find  that  the  mark  for  three  feet  must  be  between  2  and  4. 
This  is  placed  at  the  starting-point  and  the  3  ft.  and  7f "  found 
as  before,  only  to  the  left. 

It  may  be  advisable  to  place  the  7f n  mark  at  the  starting- 
point  of  the  measurement  and  measure  on  to  o  and  then  to 

3  feet. 

For  a  "half-size  "  drawing,  the  32  scale  is  used,  the  divi- 
sion by  2  made  mentally. 

For  a  "double-size  drawing,"  "triple-size  drawing," 
etc.,  use  the  32  scale  and  perform  the  multiplication  mentally. 

For  a  drawing  smaller  than  ^  size,  use  the  smallest  scale, 
the  f "  =  I  foot,  and  mentally  divide  as  for  ' '  half-size  ' '  above. 

In  a  drafting-room  flat  scales  are  much  used  instead  of  the 
triangular  scale. 


USE   OF  INSTRUMENTS  1 3 

To  Use  the  Scale.— Lay  the  scale  along  the  line  to  be 
measured  so  that  the  desired  scale  is  away  from  the  body  and 
thus  in  good  light.  Adjust  the  position  of  the  marks  as 
described  above  and  mark  the  ends  of  the  dimension  obtained 
either  with  a  "  needle-pointed  "  lead-pencil,  a  pricker,  or  the 
point  of  the  bow  spacers  or  large  compass.  The  metallic 
points  are  best,  as  they  are  sharper.  Mark  the  points  distinctly ; 
send  the  metallic  points  through,  but  do  not  make  large  holes 
in  the  paper.  The  point  is  marked  distinctly  to  save  the  eyes 
when  it  is  to  be  found  and  used  later,  but  the  paper  must  not 
be  ruined  by  carelessness.  When  several  dimensions  are  to  be 
measured  along  the  same  line,  do  not  shift  the  scale  for  each 
one;  leave  it  in  the  first  position  and  make  all  the  marks. 
This  lessens  the  danger  of  making  errors. 

In  marking  these  points,  the  sharp  pencil  or  metallic  point 
should  never  mar  the  scale,  but  the  instrument  should  be  slid 
down  along  the  scale — lying  flat  against  it  if  possible. 

Triangular-scale  Guard. — This  is  of  value  when  the  same 
scale  is  used  for  any  length  of  time;  it  is  clamped  on  the 
triangular  scale  so  that  the  desired  scale  may  be  readily 
found. 

Right-line  Pen. — The  right-line  pen  is  used  for  drawing 
all  ink-lines  that  are  not  arcs  of  circles.  It  consists  essentially 
of  two  sharpened  steel  points  or  nibs  secured  firmly  together 
or  made  from  one  piece  of  steel.  The  steel  nibs  tend  to 
separate  and  are  kept  in  the  desired  position  by  means  of  the 
small  screw. 

The  ink  is  introduced  between  the  nibs  of  the  pen  by  the 
rubber-topped  ink-dropper  or  the  quill  pen  attached  to  the  cork 
of  the  bottle,  if  such  are  provided.  If  not  provided,  a  steel 
pen  is  the  best  thing  to  use.  In  filling  the  R.  L.  pen  in  any 
of  these  ways,  hold  both  the  R.  L.  pen  and  the  other  imple- 
ment nearly  vertical  and  bring  the  points  of  the  two  instruments 
together  with  the  point  of  the  other  instrument  inserted 
between  the  nibs  of  the  R.  L.  pen,  when  the  ink  will  freely 
run  into  the  R.  L.  pen. 


14  MECHANICAL   DRAWING. 

A  thin  strip  of  paper  is  sometimes  used,  but  it  is  a  bad 
practice,  as  small  portions  of  paper  may  be  caught  in  the  pen. 

Another  method  is  to  dip  the  R.  L.  pen  in  the  ink,  in 
which  case  the  outside  of  the  pen  must  be  very  carefully  wiped. 

The  ink  is  held  in  place  by  capillarity,  and  is  drawn  out  as 
the  pen  is  carried  along  the  paper. 

Ordinarily  fill  the  pen  only  to  a  height  of  one-quarter  of 
an  inch,  as  the  ink  will  probably  dry  before  being  used ;  when 
drawing  heavy  shade  lines,  fill  the  pen  as  full  as  it  will  hold 
with  ink. 

Never  fail  to  wipe  off  the  outside  of  the  nibs  of  the  pen  after 
filling  with  ink. 

Use  of  the  R.  L.  Pen. — The  pen  is  held  vertical;  the 
screw-head  away  from  the  guide;  the  middle  finger  against 


FIG.  7. 

the  opening  of  the  nibs  on  one  side  and  the  thumb  higher  up 
and  against  the  opening  of  the  nibs  on  the  other  side;  the 
upper  part  of  the  pen  resting  in  the  outer  joint  of  the  first 
finger ;  the  last  two  fingers  resting  on  the  T  square  or  triangle 
as  a  guide.  Note  carefully  Fig.  7. 


USE   OF  INSTRUMENTS.  1 5 

The  reason  for  holding  the  pen  as  described  is  that  there 
is  no  danger  of  changing  the  opening  of  the  nibs  by  greater 
or  less  pressure  put  on  them  by  the  thumb  and  fingers. 

If  the  thumb  and  fingers  press  on  the  top  and  bottom  of 
the  nibs,  the  least  change  of  this  pressure  will  cause  a  variation 
in  the  width  of  the  line,  as  in  Fig.  8. 


FIG.  8. 

By  holding  the  pen  properly,  a  line  of  equal  width,  as  far 
as  this  liability  to  error  is  concerned,  is  secured. 

The  pen  is  guided  by  the  T  square,  triangle,  or  irregular 
curve,  and  it  must  be  carefully  noted  that  these  are  for  a  guide 
only.  The  pressure  against  the  guide  must  be  light  and 
uniform,  as  a  variation  of  this  pressure  will  produce  a  variation 
in  the  width  of  the  line,  astin  Fig.  9. 


FIG.  9. 

The  proper  method  of  holding  the  pen  will  assist  in  pre- 
venting this  defect,  as  the  nibs  are  held  more  or  less  firmly  in 
position  by  the  fingers.  The  nibs  of  the  pen  must  be  kept 
parallel  to  the  guide,  as,  if  they  are  dragged  along  diagonally, 
a  ragged  line  will  be  made.  The  pen  must  not  be  held  too 
close  to  the  guide,  as  the  ink  is  likely  to  flow  out  suddenly  and 
make  a  blot  against  the  guide ;  if  held  vertical,  the  curvature 
of  the  nib  will  prevent  this  accident. 

In  drawing  ink-lines  a  positive  and  constant  pressure  must 
be  maintained  directly  downwards;  this  pressure  varies  with 
the  sharpness  of  the  pen  and  the  smoothness  of  the  paper. 
With  a  very  sharp  pen  and  very  smooth  paper  an  extremely 
light  pressure  is  required ;  but  with  a  dull  pen  and  paper  full 
of  depressions  and  heights  considerable  downward  pressure 


1 6  MECHANICAL   DRAWING. 

must  be  maintained.  This  downward  pressure  is  entirely  dis- 
tinct from  the  pressure  against  the  guide  (T-square,  triangle, 
etc.).  Each  one  by  practice  must  determine  for  himself  what 
downward  pressure  is  required  for  the  special  pen  and  paper 
used. 

Both  nibs  must  rest  on  the  paper  equally  and  must  be 
carried  evenly  along  the  guide;  if  one  nib  presses  harder  than 
the  other,  a  ragged  line  is  produced,  as  in  Fig.  10. 


6 
FIG.  10. 

a  shows  where  the  upper  nib  has  cut  a  clean,  firm  edge, 
and  b  where  the  lower  one  has  been  the  only  one  cutting  a 
sharp  edge. 

The  body  must  be  moved  about  as  necessary  when  using 
the  R.  L.  pen.  The  important  thing  is  to  make  a  good  line. 
So  the  hand  and  arm  must  be  first  arranged  and  the  body 
moved  so  as  to  leave  freedom  of  movement  to  the  arm.  When 
holding  the  pen  as  described  the  body  will  have  to  be  moved 
well  to  the  left,  so  that  instead  of  the  eye  being  directly  over 
the  line  drawn  it  will  be  looking  along  the  line  from  above  and 
to  the  left. 

Always  keep  the  arm  free  from  the  body. 

Draw  away  from  and  not  towards  the  body. 

When  drawing  ink-lines  with  the  use  of  irregular  curves  the 
pen  must  be  constantly  twisted  in  the  fingers  to  keep  the  nibs 
parallel  to  the  edge  of  the  curve.  Considerable  practice  is 
required  before  good  work  of  this  kind  can  be  done. 

The  R.  L.  pen  may  also  be  used  without  a  guide  for 
drawing  curves  when  it  is  not  desired  to  take  the  time  neces- 
sary to  find  the  exact  curved  lines  on  the  irregular  curve. 
Rest  the  last  two  fingers  on  the  board ;  carefully  follow  the 
curve  drawn  in  pencil ;  twist  the  pen  in  the  fingers  to  keep  the 


USE   OF  INSTRUMENTS.  I/ 

nibs  parallel  to  the  line  at  each  point.  This  is  especially 
valuable  in  making  irregular  breaks  in  metal,  instead  of  using 
the  writing-pen,  which  never  makes  clean  work. 

Always  draw  lines  from  left  to  right.  If  it  should  be 
necessary  to  go  over  a  line  a  second  time,  go  over  it  in  the 
same  direction  as  before.  Never  go  backwards  on  a  line. 

In  case  the  ink  does  not  flow  readily  from  the  pen,  a  quick 
method,  though  an  inadvisable  one,  is  to  run  the  point  across 
one  of  the  fingers  of  the  left  hand.  A  better  way  is  to  keep  a 
small  piece  of  moistened  blotting-paper  at  hand  and  touch  the 
point  of  the  pen  to  that;  if  the  ink  fails  to  run  then,  clean  the 
pen  and  refill  it.  On  a  dry  day  the  pen  must  be  frequently 
cleaned  on  account  of  the  rapid  evaporation  of  the  dissolving 
liquid. 

Sometimes  the  ink  may  be  made  to  flow  by  pressing  the 
pen  with  a  blade  flat  on  the  paper,  using  enough  pressure  to 
cause  the  blades  to  slide  on  each  other.  This  breaks  the  small 
clot  of  ink  at  the  point. 

Always  test  the  R.  L.  pen  by  drawing  lines  against  a 
guide,  as  it  is  never  possible  to  tell  surely  what  kind  of  a  line 
will  be  made  by  testing  the  pen  unguided. 

Frequent  cleaning  of  the  pen  is  one  of  the  secrets  of  making 
clear  lines. 

Especial  care  should  be  given  to  cleaning  the  R.  L.  pens  ; 
they  should  be  cleaned  after  use,  even  if  only  five  minutes  will 
intervene  before  using  them  again ;  they  should  never  be  put 
away  uncleaned. 

A  piece  of  cotton  cloth  or  chamois-skin  will  thoroughly 
clean  the  pen;  nearly  close  the  nibs  and  insert  the  cloth 
between  the  nibs  and  draw  it  through.  If  the  ink  is  fresh  and 
this  operation  be  repeated  two  or  three  times,  the  pen  will  be 
cleaned.  It  is  well  to  dip  the  pen  in  water  before  cleaning. 

Do  not  use  too  thick  a  piece  of  cloth  or  chamois-skin,  as 
the  nibs  of  the  pens  may  snap  off. 

To  keep  all  the  lines  of  the  same  kind  of  the  same  width, 


1 8  MECHANICAL    DRAWING. 

do  not  change  the  adjustment  of  the  pen  in  cleaning ;  draw  the 
cleaning  cloth  between  the  points  carefully  without  moving  the 
screw. 

Do  not  use  a  bad  pen.  If  one  line  is  bad,  find  the  cause 
at  once.  Sharpen  the  pen;  clean  it  out;  or  get  new  ink,  as 
necessary. 

To  Examine  and  Test  the  R.  L.  Pen. — Note  the  shape  of 
the  nibs  of  the  pen  when  new,  and  always  make  them  of  that 
shape  when  sharpening  the  pen.  The  nibs  should  be  of 
exactly  the  same  shape  and  length.  Look  along  the  edges  of 
the  nibs,  holding  the  pen-point  towards  the  eye  and  turning 
the  pen  in  the  plane  of  the  nibs,  and  note  if  any  portions  of  the 
points  are  blunt.  The  bluntness  will  appear  as  a  line  of  light 
along  the  point. 

To  Test.  — Fill  the  pen  with  ink  and  open  the  nibs  so  as  to 
make  a  wide  line.  Begin  to  draw  the  line  along  a  T  square 
or  triangle  and  note  whether  the  nibs  cut  equally.  Effects  like 
those  in  Fig.  1 1  will  be  observed  as  the  nibs  are  opened  and 


FIG.  ii. 

closed  until  the  proper  setting  is  found.  Then  if  the  marks 
of  the  nibs  at  the  left  are  equally  strong,  the  nibs  are  of  equal 
length. 

Test  for  sharpness  by  drawing  fine  lines. 

To  Sharpen  the  R.  L.  Pen. — Place  oil  or  water  as  required 
on  the  stone.  Screw  the  nibs  of  the  pen  together  until  they 
firmly  touch.  Hold  the  pen  in  a  plane  perpendicular  to  the 
oil-stone,  the  opening  of  the  nibs  in  that  plane,  and  move  it 
back  and  forth  along  the  stone,  changing  the  slope  of  the  pen 
one  way  and  the  other  as  it  is  moved  along  the  stone,  so  as  to 
grind  off  the  points  to  the  proper  curve  and  also  to  make  them 
of  the  same  length.  This  makes  both  points  dull,  but  they 
are  of  equal  length.  Next,  clean  the  pen  and  open  the  nibs; 
examine  the  pen  as  described  before  and  note  what  parts  of  the 


USE   OF  INSTRUMENTS.  1 9 

points  need  most  sharpening.  Of  course  the  widest  light  por- 
tions are  the  dullest.  Close  the  nibs  until  they  just  touch,  and 
proceed  to  sharpen  as  follows :  Place  one  of  the  nibs  on  the 
stone,  the  pen  at  an  angle  of  about  15°.  Move  the  pen  back- 
wards and  forwards  along  the  stone,  at  the  same  time  twisting 
it  in  the  ringers.  This  brings  the  edges  of  the  nibs  in  position 
to  be  ground  down  as  required.  Sharpen  principally  the  por- 
tions noted  as  dull.  Frequently  clean  the  pen  and  examine 
as  before.  Continue  the  operation  until  no  dull  places  can  be 
discovered.  Clean  thoroughly  and  test  the  pen  with  ink.  If 
not  properly  sharpened,  continue  as  before  until  exactly  right. 
In  sharpening,  it  is  likely  that  one  nib  may  be  sharpened  too 
much  and  thus  become  too  short;  in  that  case  the  ink-line 
drawn  will  show  the  defect,  and  it  will  be  necessary  to  again 
dull  the  points  and  begin  over  again.  Practice  soon  brings 
efficiency,  and  nobody  can  properly  sharpen  a  pen  for  another, 
as  no  two  people  hold  the  pen  in  precisely  the  same  way.  It 
is  very  important,  then,  for  each  one  to  persevere  and  learn 
to  sharpen  his  pen. 

Be  very  careful  about  using  the  stone  on  the  inside  of  the 
nibs.  If  a  feather-edge  be  formed  in  sharpening  the  pen,  open 
the  nibs  and  slip  the  stone  between  them.  A  very  few  and 
slight  movements  of  the  stone  will  take  away  the  feather-edge. 

There  is  a  limit  to  the  sharpness  of  pen  required,  as  the 
paper  will  be  cut  and  ruined  if  the  pen  is  too  sharp.  Trial 
only  will  test  for  this  defect,  and  it  is  a  very  simple  matter  to 
dull  the  pen  slightly,  as  explained. 

Compasses. — This  instrument  is  used  for  drawing  arcs  of 
circles  in  pencil  or  ink,  from  the  largest  that  can  be  made  with 
the  extension  bar  inserted  to  a  circle  of  about  I J"  in  diameter. 
It  is  an  extremely  accurate  instrument  and  should  be  well 
treated.  The  needle-point  is  fixed ;  either  the  pencil-  or  pen- 
point  may  be  put  in  place  and  clamped  with  the  screw.  These 
points  should  always  be  pushed  home  and  carefully  clamped; 
and  pushed  or  pulled  straight  when  placing  or  removing  them. 


2O  MECHANICAL   DRAWING. 

To  set  the  needle-point,  put  in  place  the  pen-point;  close 
the  instrument  and  push  the  needle-point  out  until  the  shoulder 
at  the  base  of  the  needle  just  coincides  with  the  point  of  the 
pen ;  then  clamp  the  needle-point.  Once  the  needle-point  is 
adjusted,  it  need  never  be  changed. 

To  set  the  pencil-point,  insert  the  pencil-point  in  the  com- 
passes and  push  it  home  and  clamp  in  position ;  push  the 
pencil  out  until  it  coincides  with  the  shoulder  of  the  needle- 
point and  clamp  the  pencil.  As  the  pencil  is  resharpened,  it 
must  be  pushed  out  to  agree  again  with  the  shoulder  of  the 
needle-point. 

NOTE. — The  pencil-point  is  sharpened  as  described  under 
the  methods  of  sharpening  leads,  making  the  chisel-point 
narrow. 

To  Test  the  Compasses. — Insert  the  pen-point  and  close 
the  instrument.  The  needle-point  and  the  middle  of  the  pen 
should  coincide.  The  same  should  apply  to  the  pencil-point, 
except  that  allowance  must  be  made  for  inaccuracy  in  sharpen- 
ing the  lead.  Another  test  for  the  compasses:  Place  the  pen- 
point  in  place ;  break  the  knees  of  both  legs  of  the  instrument 
and  open  the  legs  until  the  angle  at  the  upper  part  is  about 
45°  and  bring  the  points  together;  these  should  closely 
coincide. 

To  Use  the  Compasses. — From  the  given  center  the  radius 
to  be  used  is  measured  with  the  triangular  scale  and  sharply 
and  clearly  marked.  Carefully  place  the  needle-point  of  the 
compasses  exactly  in  the  center  of  the  mark  for  the  given 
center  and  push  it  home  to  the  shoulder.  This  fixes  the 
center  so  that  it  may  be  found  again  when  needed,  and  also 
gives  the  needle-point  a  firm  support  in  the  wood  under  the 
paper  and  preserves  the  paper.  This  needle-point  must  always 
be  kept  upright  by  bending  the  knee  above  it  as  much  as  is 
necessary  for  whatever  circle  is  drawn.  This  is  very  impor- 
tant. Next,  open  the  legs  of  the  compasses  and  bend  the 
knee  above  the  needle-point  as  required,  and  also  the  knee 


USE   OF  INSTRUMENTS.  21 

above  the  pencil-point,  until  both  needle-  and  pencil-points  are 
vertical.  This  may  be  approximated  to  with  the  pencil-point, 
but  must  be  carefully  done  for  the  needle-point.  When  the 
pencil-point  is  nearly  over  the  point  measured,  spring  the 
instrument  open  as  required  until  the  pencil-point  cuts  the 
middle  of  the  mark  for  the  measured  distance.  Test  it  by 
sweeping  a  short  arc  through  the  point  and  change  as  needed 
until  the  exact  center  is  cut  by  the  pencilled  arc.  Hold  the 
handle  of  the  compasses  between  the  thumb  and  first  finger, 
the  instrument  nearly  vertical ;  begin  to  draw  the  arc  at  the 
left  and  towards  the  body  at  a  point  towards  the  S.  W.  ;  lean 
the  instrument  slightly  ahead  of  the  position  of  the  pencil-point 
and  keep  the  same  amount  of  forward  slope  as  the  arc  is  swept 
around  to  the  starting-point,  always  from  W.  to  N.,  etc.,  and 
press  on  the  pencil-point  firmly  and  with  a  constant  pressure. 
Never  go  backwards  on  the  arc.  If  any  part  is  indistinct,  go 
over  it  again  in  the  same  direction. 

Make  the  line  sharp  and  clean. 

On  arriving  at  the  starting-point,  the  line  should  coincide 
exactly  with  that  part  drawn  at  the  beginning. 

The  same  methods  apply  for  inking,  the  amount  of  pres- 
sure required  on  the  pen-point  being  determined  by  experience 
for  the  kind  of  paper  used.  The  bending  of  the  knees  of  the 
compasses  in  inking  is  especially  important,  as  both  nibs  of 
the  pen  must  cut  sharply  and  equally  in  order  to  secure  a 
clean,  sharp  line. 

At  each  change  of  opening  of  the  compasses,  before  making 
a  line  on  the  drawing,  a  test  should  be  made  on  the  margin 
of  the  paper  to  see  that  a  good  line  will  be  drawn.  *  - 

The  remarks  under  R.  L.  pen  in  regard  to  cleaning  the 
pen  apply  with  equal  force  to  the  compass-pen. 

Extension-bar. — When  the  arc  to  be  drawn  is  large,  the 
extension-bar  is  put  in  place  above  the  pencil-  or  pen-point, 
care  being  taken  that  it  and  the  pencil-  or  pen-point  are  both 
pushed  home  and  clamped. 


22  MECHANICAL   DRAWING. 

In  drawing  arcs  with  the  extension-bar  in  use,  it  is  some- 
times necessary  to  guide  the  pencil-  or  pen-point  with  one  hand 
while  steadying  and  turning  the  compasses  with  the  other  hand 
on  the  handle. 

If  a  "beam  compass"  is  available,  it  should  be  used 
instead  of  the  compass  with  the  extension-bar  for  inking,  as 
the  latter  springs  considerably. 

Bow  Spacers. — The  bow  spacers  are  used  for  spacing  oft 
distances  of  equal  length.  The  points  are  also  much  used  for 
marking  measured  points  instead  of  using  a  "  needle-pointed  " 
lead-pencil,  as  the  point  of  the  spacer  is  much  finer  than  can 
be  maintained  on  any  lead-pencil. 

Instead  of  using  the  spacers  for  laying  off  distances  of  equal 
lengths,  it  is  more  accurate  to  lay  the  triangular  scale  along 
the  line  and  mark  the  divisions.  Although  some  of  the  divi- 
sions thus  laid  off  may  be  inaccurate,  the  total  length  will  be 
true  and  there  is  less  liability  of  error.  When  dimensions  are 
not  on  the  triangular  scale,  the  bow  spacers  are  used  with 
advantage  and  are  useful  in  dividing  a  line  into  any  given 
number  of  parts  quickly,  when  it  is  not  desired  to  take  the  time 
necessary  to  divide  the  line  geometrically. 

In  dividing  a  line  into  parts  geometrically,  the  bow  spacers 
are  useful  in  laying  off  quickly  and  accurately  the  equal  lengths 
on  the  line  laid  off  at  an  angle  with  the  given  line. 

Constantly  keep  the  index-finger  of  the  right  hand  on  the 
top  of  the  spacers  and  step  otf  the  points  along  the  line  to  be 
spaced,  using  the  thumb  and  second  finger  to  swing  the  instru- 
ment. The  steps  are  made  by  swinging  the  points  of  the 
spacer  alternately  one  way  and  then  the  other,  pushing  each 
point  in  sufficiently  to  mark  the  point  well.  This  necessitates 
a  forward  and  backward  movement  of  the  hand  for  each  point 
marked,  combined  with  the  swinging  movements  of  the  points. 
of  the  spacers. 

If  a  distance,  as  2  inches,  is  to  be  spaced  off  into  any 
number  of  divisions,  say  ten,  estimate  with  the  eye  about  the 


USE    OF  INSTRUMENTS.  23 

length  of  one  division  and  set  the  spacer.  Go  over  the  line 
quickly,  making  the  least  amount  of  puncture  possible.  The 
amount  under  or  over  at  the  end  is  again  divided  by  estimate 
and  the  spacers  reset  and  another  trial  made  very  lightly. 
When  the  exact  setting  is  found,  go  over  the  line  again  and 
puncture  the  paper  sufficiently  to  clearly  mark  the  divisions. 

Bow  Pencil  and  Bow  Pen. — These  instruments  are  very 
useful  and  are  extremely  accurate  when  handled  carefully  and 
kept  in  good  order. 

They  are  used  for  small  arcs. 

The  needle-points  are  adjusted  and  the  instruments  tested 
as  given  under  compasses,  noting  that  the  flattened  side  of 
the  needle-point  is  placed  towards  the  pen-  or  pencil-point  so 
that  very  small  circles  may  be  drawn. 

In  using  these  instruments,  the  needle-points  are  always 
pressed  in  to  the  shoulder,  as  stated  under  Compasses ;  by 
testing  the  setting  with  a  small  arc  and  slightly  changing  the 
screw,  very  accurate  adjustments  can  be  made. 

The  remarks  under  Compasses  apply  as  to  leaning  the 
instrument  a  little  forward  and  putting  a  certain  and  constant 
amount  of  pressure  on  the  point ;  also  in  regard  to  the  point  of 
beginning  to  draw  the  circle. 

In  opening  and  closing  these  instruments,  press  the  points 
together  with  the  left  thumb  and  forefinger,  thus  removing  the 
pressure  from  the  adjusting-nuts  before  turning  them;  this 
preserves  the  threads  of  the  adjusting-screws  and  makes  the 
operations  more  rapid. 

Since  there  are  no  knees  to  be  bent  in  the  bow  instruments, 
the  nibs  of  the  pen-points  do  not  evenly  touch  the  paper  for 
all  radii,  and  the  largest  and  smallest  circles  may  not  be  as 
good  as  the  medium-sized  ones  drawn.  When  the  needle-point 
is  set  as  stated  above,  it  is  right  for  the  average  of  radii  used, 
but  it  may  be  necessary  to  change  the  needle-point  for  very 
small  or  very  large  arcs. 

In  Fig.  1 2,  a  represents  the  positions  of  the  nibs  of  the  pen 


24  MECHANICAL   DRAWING. 

for  the   average  arcs;   b   for   the   very  small;    and  c  for   the 
largest.     The  needle   must  be  pushed  in  for   b  and   out  for 
a          6         c, 

it     //     \\ 

FIG.  12. 

c,  in  order  to  have  the  nibs  cut  equally  and  produce  a  per- 
fect line. 

The  remarks  under  R.  L.  Pen  in  regard  to  cleaning  the 
pen  apply  with  equal  force  to  the  bow  pen. 

Dividers. — This  instrument  has  two  sharp  points,  and  is 
used  on  the  drawing-board  for  marking  off  distances  that  are 
too  great  for  the  bow  spacers ;  and  very  largely  on  charts  in 
making  measurements. 

The  clamp  at  the  top,  when  set,  ensures  no  change  in  the 
opening  of  the  instrument.  Many  draftsmen,  however,  object 
to  this  clamp  and  consider  that  a  properly  made  joint  carefully 
handled  will  never  slip.  The  small  adjusting-screw  on  one  of 
the  legs  enables  most  accurate  work  to  be  done.  This  is 
called  the  hair-spring  adjustment. 

t  To  Use  the  Dividers. — Ease  the  clamp-screw  at  the  head 
of  the  instrument;  open  the  legs  until  the  points  are  slightly 
wider  apart  than  the  required  distance;  set  the  clamp-screw 
at  the  head;  with  the  "  hair-spring  "  adjusting-screw  close  the 
movable  point  the  required  amount. 

Distances  must  never  be  taken  from  the  triangular  scale 
with  these  instruments,  as  the  points  will  ruin  the  scale;  and 
this  way  is  not  as  accurate  as  the  correct  method. 

Always  lay  the  triangular  scale  on  the  drawing-board  and 
measure  off  the  desired  distance,  marking  it  by  means  of  one 
of  the  points  of  the  bow  spacers,  or,  better  still,  with  one  of 
the  points  of  the  dividers,  or  a  pricker.  As  the  inner  sides  of 
the  divider  legs  are  flattened,  these  flat  portions  may  be  slid 
along  down  the  triangular  scale  and  the  points  accurately 
marked. 

Take   care  not  to   unscrew  the   ' '  hair-spring  ' '   adjusting- 


USE    OF  INSTRUMENTS.  2$ 

screw  too  much,  as  the  screw  will  become  detached  from  the 
point  and  the  spring  may  be  broken. 

The  dividers  should  always  have  the  adjusting-screw  of  the 
*'  hair-spring  "  screwed  "home  "  when  put  away. 

Irregular  Curves. — These  are  guides  for  drawing  lines  that 
are  neither  straight  nor  arcs  of  circles.  When  a  series  of 
irregular  points  are  found  through  which  a  line  is  to  be  drawn, 
begin  with  some  definite  point  and  pick  out  the  portion  of  any 
one  of  the  irregular  curves  that  seems  most  likely  to  fit  for  the 
greatest  length.  Test  by  laying  this  curved  part  along  the 
line  of  points,  moving  the  curve  about;  and,  if  necessary, 
trying  other  curves  until  the  longest  correct  one  is  found. 
Draw  in  pencil  the  curved  line  until  nearly  to  the  end  of  the 
part  that  fits  accurately.  Never  draw  the  line  quite  to  the  end 
of  the  unison  of  the  curves.  Before  removing  the  irregular 
curve  from  its  position,  make  on  it  faint  pencil-marks  defining 
the  beginning  and  end  of  the  portion  drawn,  and  also  make 
corresponding  marks  on  the  paper.  Then  remove  the  curve. 
The  portion  used  may  then  be  readily  found  when  inking. 

If  the  curved  figure  is  a  regular  one,  a  reverse  curve  exactly 
corresponding  to  the  one  drawn  will  be  required  somewhere  in 
the  figure.  This  curve  may  be  marked  on  the  irregular  curve 
by  carrying  the  marks  placed  there  across  the  narrow  edge  and 
to  the  under  side,  where  the  corresponding  marks  may  be  made. 
Then  this  curve  will  fit,  if  the  right  mark  is  placed  at  the  point 
exactly  opposite  the  original  definite  point  of  starting. 

From  the  end  of  the  curve  drawn,  carry  on  as  far  as  possible 
a  new  curve,  and  continue  until  the  entire  curve  is  drawn. 

It  is  especially  important  never  to  draw  the  curves  quite  to 
the  point  of  separation  of  the  required  curve  and  the  one  on  the 
irregular  curve,  as  it  will  be  found  difficult  to  begin  a  new  por- 
tion of  curve  exactly  in  agreement  with  the  one  ended.  This 
is  the  most  difficult  part  of  the  use  of  the  irregular  curves — to 
have  the  end  of  the  one  and  the  beginning  of  the  other  line  in 
unison. 


26  MECHANICAL   DRAWING. 

In  pencilling  and  inking  with  the  irregular  curves  as  guides, 
the  pencil  or  pen  must  be  turned  in  the  fingers  so  as  to  be 
tangent  to  the  curve  drawn  at  all  points. 

Where  the  irregular  curve  already  contains  numerous 
pencil-marks,  the  new  marks  may  be  connected  by  lines  for 
certainty  of  finding  them  when  inking. 

If  the  points  through  which  the  curve  is  to  be  drawn  are 
far  apart,  it  is  often  well  to  lightly  pencil  the  curve  free-hand 
and  then  draw  the  portions  of  it  in  pencil  with  the  aid  of  the 
irregular  curve ;  but  never  fail  to  draw  in  pencil  first,  and  mark 
the  irregular  curve  for  inking.  Do  not  attempt  to  draw  the 
curve  in  ink  without  pencilling  it  first. 

For  small  curves  it  is  often  a  good  plan  to  cut  a  special 
curve  from  a  thin  strip  of  wood  or  from  a  card  that  is  sufficiently 
thick  and  stiff. 

Protractors. — These  are  used  for  laying  off  angles.  They 
are  seldom  used  in  machine  drawing,  but  are  largely  used  in 
surveying  work  of  all  kinds. 

The  protractors  should  not  be  used  on  the  drawing-board 
for  angles  that  can  be  made  by  the  aid  of  the  triangles. 

There  are  many  forms  of  these  instruments,  from  the  heavy 
metal  frame  with  the  swinging  arms  to  the  plain  metal,  horn, 
or  celluloid  article ;  for  ordinary  drafting-room  work  the  plain 
metal,  horn,  or  celluloid  kind  answers  all  purposes,  as  the 
number  of  degrees  of  irregular  angles  would  be  stated  on  the 
drawing. 

How  to  Use  the  Protractors. — Place  the  180°  marks  at 
either  side  of  the  arc  (not  necessarily  at  the  end  of  the  arc)  on 
the  base  line  from  which  the  angle  is  to  be  measured,  and  slide 
the  protractor  along  until  the  notch  or  mark  in  the  middle  of 
the  base  coincides  with  the  vertex  of  the  angle.  Mark  at  the 
outer  circumference  the  point  through  which  the  line  defining 
the  angle  is  to  be  drawn,  noting  that  the  inner  marks  read 
from  one  end  of  the  arc,  and  the  outer  from  the  other.  Re- 
move the  protractor  and  draw  the  line. 


USE  OF  INSRTUMENTS.  27 

Erasers. — The  rubber  ink-eraser  should  be  used  very 
carefully  on  the  drawing-board.  It  erases  only  a  little  more 
rapidly  than  the  rubber  pencil-eraser  and  is  likely  to  ruin  the 
surface  of  the  paper  so  that  it  is  very  difficult  to  make  a  good 
ink-line  afterwards.  With  a  good  quality  of  paper  it  may  be 
used  with  comparative  safety.  The  surface  must  be  well 
polished  afterwards. 

For  erasing  on  tracing-cloth,  the  ink-eraser  only  should 
be  used.  Afterwards  the  surface  should  be  rubbed  with  a  soap- 
stone  pencil  and  well  polished. 

When  an  error  is  made  or  work  in  ink  is  to  be  removed 
for  any  reason,  use  the  rubber  pencil-eraser  and  the  erasure 
may  be  made  and  a  good  line  drawn  afterwards.  Time 
and  light  pressure  are  required,  but  the  line  will  be  removed 
eventually.  As  the  small  particles  of  paper  removed  become 
electrified,  it  is  necessary  to  remove  them  occasionally  by 
brushing  with  the  back  of  the  fingers  or  a  cloth;  after  the 
ink-line  is  removed,  rub  the  paper  with  some  smooth,  hard 
substance  like  the  handle  of  the  metal  ink-eraser  or  the  end  of 
a  knife-handle  or  a  smooth  piece  of  ivory  or  agate.  After 
that  a  new  line  may  be  drawn  with  safety.  When  the  new 
ink-line  is  to  be  a  heavy  one,  it  is  well  to  draw  it  in  parts ;  in 
each  portion  have  the  pen  closed  for  a  comparatively  fine  line, 
and  allow  it  to  dry  before  drawing  the  next  width  of  the  line. 

The  metal  eraser  should  never  be  used  when  a  new  line  is 
to  be  drawn.  It  is  used  to  remove  errors  where  an  ink-line  is 
drawn  past  the  required  point.  It  must  then  be  used  with 
great  care.  Use  this  eraser  with  the  hand  above  the  handle 
and  the  fingers  and  thumb  well  down  towards  the  point.  This 
is  to  prevent  the  sharp  point  of  the  metal  from  touching  the 
paper,  as  there  is  no  way  of  telling  how  deeply  this  point  may 
cut.  The  flat  of  the  knife-point  only  must  be  allowed  to  do 
the  erasing. 

Hold  the  eraser  as  described  and  make  a  fine,  light  cut  at 
the  point  where  the  error  begins,  and  then  draw  the  small 


28  MECHANICAL   DRAWING. 

amount  of  the  surface  of  the  paper  cut  through  away  from  the 
good  line.  This  leaves  a  clearly  defined  line  as  an  ending  of 
the  good  work.  After  that  the  erasure  may  be  carried  on  by 
drawing  the  flat  edge  of  the  eraser  gently  along  the  paper. 

In  case  a  line  may  be  too  broad,  it  may  be  made  narrower 
by  the  use  of  this  eraser.  Begin  at  one  end  of  the  too  heavy 
portion  of  the  line  and  make  a  fine  cut  as  described,  continuing 
the  cut  carefully  along  the  line  and  making  the  line  of  the 
desired  width.  Then  each  portion  may  be  drawn  away  gently 
with  the  eraser  as  described. 

The  black,  sponge  rubber  is  used  for  cleaning  the  drawing 
after  it  is  completed.  This  is  rubbed  across  the  drawing 
gently  after  all  the  pencil-lines  have  been  erased  by  the  rubber 
pencil-eraser.  This  rubber  will  simply  clean  off  the  dust  and 
discolorations  made  by  the  hands  and  instruments.  In  using 
it,  however,  do  not  rub  longer  than  absolutely  necessary  at 
any  part  of  the  drawing,  as  it  will  dull  the  ink  effect.  Especial 
care  should  be  taken  at  parts  pf  the  drawing  where  the  ink 
work  is  heavy,  as  its  effect  will  be  seriously  marred. 

The  best  cleanser  for  the  drawing-paper  is  stale  bread  that 
is  not  too  dry. 

Erasing-shields. — These  are  of  thin  metal  with  small 
openings  of  various  shapes  that  will  fit  over  small  portions  of 
the  drawings  to  allow  of  erasing  just  what  is  desired  and  no 
more. 

Horn  Centers.— These  instruments  are  used  when  a  great 
many  circles  are  to  be  drawn  from  the  same  center.  They 
should  never  be  used  except  when  absolutely  necessary.  If 
the  compasses  are  fairly  bent  as  described  and  the  bending  is 
done  for  each  circle  of  varying  radius,  the  center  in  the  paper 
will  generally  last  as  long  as  is  required.  In  case  the  center 
in  the  paper  is  enlarged  or  torn,  the  horn  center  must  be  used, 
but,  as  a  rule,  it  is  a  sign  of  carelessness  if  a  horn  center 
appears  on  the  drawing-board.  Of  course,  in  special  drawings, 
where  trams  are  used,  or  in  line'  shading,  the  horn  center  is 


USE   OF  INSTRUMENTS.  2$ 

absolutely  necessary,  but  not  in  the  ordinary  work  of  the  draft- 
ing-room. 

In  using  the  horn  center,  it  is  placed  with  its  center  as 
nearly  over  the  required  point  as  possible,  and  is  pushed  down 
until  the  three  points  on  the  under  side  are  firmly  imbedded  in 
the  paper  and  wood;  in  other  words,  it  is  pushed  "home." 
Then,  great  care  must  be  taken  that  the  point  of  the  compass 
is  placed  on  the  horn  center  directly  over  the  correct  point. 

In  place  of  the  horn  center  small  pieces  of  thin  transparent 
substances  such  as  isinglas  or  sheet  gelatine  are  used.  •  These 
have  no  points  on  the  under  side  and  depend  on  the  friction  of 
the  paper  for  their  position.  These  materials  are  used  only 
when  an  especially  handsome  drawing  is  to  be  made  and  it  is 
desired  that  no  holes  shall  be  made  in  the  paper  by  the  points 
of  the  horn  center.  Ordinarily  the  horn  center  is  used. 

To  Use  Isinglas  or  Sheet  Gelatine. — Cut  up  into  pieces 
about  £•''  square.  Make  a  hole  in  the  middle  with  a  shouldered 
needle  and  turn  the  needle  a  few  times  so  it  will  be  loose ; 
moisten  the  under  side  of  the  isinglas  until  it  is  quite  soft ;  then 
press  it  on  the  spot  where  required,  using  the  projecting  needle- 
point as  a  guide;  press  it  hard  against  the  paper  until  it 
adheres;  remove  the  needle-point;  and  then  with  the  agate 
polisher  press  the  surface  of  the  isinglas  center  down  until  it  is 
flush  with  the  surface  of  the  paper.  This  prevents  the  T  square 
from  lifting  it  from  its  position. 

Brushes. — These  are  of  camel's  hair.  Their  uses  are 
described  under  "Shading." 

Pricker. — This  is  practically  a  needle-point  set  in  a  handle, 
and  is  made  of  various  forms.  It  is  used  in  marking  off 
dimensions.  Press  downward  with  a  twist;  this  gives  better 
control. 

Beam-compasses  or  Trams. — These  are  flat,  wooden  rods 
of  various  lengths  with  two  clamps  that  may  be  secured  at  any 
points  of  the  length.  One  clamp  contains  a  "center,"  and 
the  other  either  a  pencil-  or  pen-point.  They  are  used  for 
drawing  large  arcs. 


30  MECHANICAL  DRAWING. 

Foot  Rule. — This  is  used  in  sketching,  dimensions  taken 
to  the  nearest  thirty-second. 

Calipers. — These  are  of  two  kinds,  outside  and  inside, 
used,  as  the  names  imply,  for  measuring  outside  and  inside 
distances  when  a  rule  cannot  be  used.  They  are  used  particu- 
larly for  finding  the  diameters  of  cylinders. 

In  measuring  the  diameter  of  a  cylinder  use  the  bent 
calipers ;  open  the  calipers  until  they  are  slightly  larger  than 
the  diameter  of  the  cylinder;  bring  them  to  the  diameter  by 
gently  tapping  them  on  the  outside  or  inside  of  the  legs  as 
necessary.  Hold  the  calipers  loosely  in  the  fingers  and  as 
nearly  as  possible  at  right  angles  to  the  work  being  measured, 
and  above  the  work  if  possible,  so  that  the  calipers  will  them- 
selves assume  the  position  where  the  measurement  is  least. 
Raise  and  lower  them  slowly  and  adjust  them  until  a  very 
slight  touch  is  obtained.  To  measure  the  distance  thus  found, 
place  the  calipers  on  the  foot  rule  with  the  flat  face  at  the  end 
of  one  leg  just  against  the  end  of  the  rule  and  in  line  with  the 
marks  for  the  sixteenths ;  the  measurement  may  be  read  from 
the  flat  face  of  the  other  leg. 

The  inside  calipers  are  the  straighter  ones  and  are  used  in 
the  same  way  in  the  interior  of  an  opening,  but  the  flat  surfaces 
at  the  ends  of  the  legs  are  now  facing  away  from  each  other. 
To  measure  the  distance  found,  lay  the  calipers  on  the  foot  rule 
so  that  the  flat  face  at  the  end  of  one  leg  rests  along  the  side 
of  the  rule  and  in  line  with  the  marks  for  the  sixteenths  and  at 
one  of  the  inch-marks ;  the  measurement  is  read  from  the  flat 
face  at  the  end  of  the  other  leg.  It  is  best  not  to  bring  the 
first  leg  to  the  end  of  the  rule,  as  it  is  difficult  to  determine 
when  it  exactly  agrees  with  the  edge.  By  standing  rule  and 
calipers  on  a  flat  surface,  of  course,  the  edge  may  be  used, 
but  the  other  method  is  sufficiently  accurate.  It  is  found  that 
the  sense  of  touch  becomes  rapidly  and  accurately  developed 
in  using  the  calipers,  and  that  dimensions  found  in  this  way 
are  reliable. 


USE   OF  INSTRUMENTS.  3 1 

Splines. — These  are  thin  strips  of  wood  or  rubber  that  are 
held  in  place  by  weights,  and  are  used  for  drawing 
irregular  curves  when  they  are  long   and  it  is  not 
convenient    to  use    the    irregular    curves    furnished. 
The  section  of  the  spline  is  shown  in  Fig.   13. 

Spline-weights    of   lead    with    metal    projecting 
wires  called   "fingers"   are    used    for    holding  the 
splines.       The  fingers  project  from  the  ends  of  the  weights, 
and  the  ends  of  the  fingers  are  thinned  and  fit  into  the  space  in 
the  top  of  the  splines,  thus  holding  the  easily  bent  splines  in 
any   desired  position.      This  leaves  the  surface  of  the  spline 
away  from  the  weights  free,  so  that  this  edge  may  be  fitted 
to  any  curve  and  lines  may  be  drawn. 

Lead-wire. — This  is  used  for  sketching  whenever  a  peculiar 
contour  is  to  be  copied.  The  wire  is  bent  to  fit  the  outline  to 
be  copied,  and  marks  are  made  at  certain  fixed  points  that  may 
be  found  on  the  drawing-board.  The  wire  is  carried  to  the 
board  and  the  outline  copied.  These  are  used  only  in  one 
plane. 

Paper-cutters, — These  are  special  devices  for  cutting  the 
paper  from  the  drawing-board,  but  the  knife  answers  all  pur- 
poses. 


GENERAL    DIRECTIONS. 

Stretching  Paper.  —  For  ordinary  work,  the  paper  is 
secured  on  the  drawing-board  with  thumb-tacks,  as  described. 
For  complicated  drawings  and  for  those  to  be  tinted,  the  paper 
is  stretched  on  the  board. 

Prepare  the  drawing-board  by  removing  all  old  paper  and 
glue,  and  see  that  the  surface  where  the  paper  is  to  be  placed 
is  smooth  and  has  no  holes. 

Raise  the  sheet  of  paper  and  look  through  it  to  the  light 
and  find  the  water-mark  or  other  mark  of  the  manufacturer. 
When  the  paper  is  held  so  that  the  name  may  be  read  properly, 
the  nearest  surface  of  the  paper  is  the  one  on  which  to  draw. 
Lay  the  paper  drawing  side  up  on  the  drawing-board.  At 


FIG.  14.  FIG.  15. 

each  corner  either  make  a  diagonal  cut  about  an  inch  long,  as 
in  Fig.  14,  or  cut  out  a  small  square  about  three-quarters  of 
an  inch  either  way,  as  in  Fig.  15. 

With  the  fingers,  turn  up  the  edges  of  the  paper  along  one 
of  the  longer  sides  about  £ "\  repeat  on  the  other  longer  side ; 
then  turn  up  the  narrow  edges  in  the  same  manner.  Turn  the 
paper  over  and  let  it  rest  on  these  edges.  With  a  sponge  or 

32 


GENERAL   DIRECTIONS.  33 

damp  cloth  thoroughly  moisten  the  paper  except  the  edges 
now  turned  down.  .The  paper  will  absorb  a  large  amount  of 
water.  The  object  is  to  have  the  paper  equally  wet  all  over, 
and  especial  care  must  be  taken  to  moisten  the  corners. 
Carefully  keep  the  bent  edges  dry.  After  the  paper  is  soaked 
well,  turn  it  over  and  place  it  in  the  most  central  part  of  the 
board.  With  a  brush  lay  the  paste  or  other  adhering  sub- 
stance evenly  along  the  turned  edge  of  one  of  the  longer  sides 
of  the  paper.  A  paste  made  of  dextrine  and  water  is  excellent 
when  the  board  is  unvarished.  Press  this  edge  firmly  down 
on  the  wood,  rubbing  it  along  from  the  center  to  either  edge 
with  the  fingers  or  a  smooth  substance.  This  tends  to  stretch 
this  edge  somewhat.  Treat  the  edge  of  the  opposite  longer 
side  of  the  paper  with  the  paste  and  lay  that  down  as  before. 
After  this  edge  has  begun  to  stick,  begin  at  the  middle  of  the 
length  and  draw  on  the  edge  with  the  fingers,  endeavoring  to 
stretch  it  tauter  by  pulling  directly  away  from  the  edge  already 
pasted,  constantly,  at  the  same  time  advancing  the  hands  from 
the  center  towards  one  edge,  while  holding  fast  all  the  stretch 
obtained.  Then  work  from  the  center  towards  the  other  edge. 
The  object  is  to  stretch  the  paper  across  the  board  and  at  the 
same  time  to  stretch  the  edge  lengthwise.  After  this  edge  is 
pasted,  treat  the  sides  in  the  same  manner. 

After  this  go  over  the  entire  board  and  draw  the  edges, 
endeavoring  still  further  to  stretch  the  paper.  The  point  is  to 
draw  and  hold  until  pasted.  Often  large  wrrinkles  may  be 
drawn  out  of  the  paper  in  this  manner.  When  stretched,  leave 
the  board  in  a  horizontal  position  to  dry.  In  a  few  hours  it 
will  be  found  that  the  paper  will  be  stretched  taut. 

A  more  rapid  and  very  successful  method  is  as  follows: 
Place  the  sheet  of  paper  in  a  vessel  of  water  and  allow  it  to 
become  thoroughly  soaked  and  thus  enlarged.  Remove  the 
paper  and  allow  the  loose  water  to  drain  off.  Place  the  paper 
on  the  board  right  side  up.  Wipe  with  a  towel  or  other  cloth 
along  the  edges  to  be  pasted,  drying  them  as  much  as  possible. 


34  MECHANICAL   DRAWING. 

Apply  the  paste  and  press  the  paper  on  the  board.  No  cutting 
of  corners  is  required,  and  no  stretching  the  paper  by  pulling 
along  the  sides.  When  dry  the  paper  will  be  well  stretched. 

The  board  with  the  wet  paper  should  be  kept  in  a  horizon- 
tal position  until  the  paper  is  dry. 

In  damp  weather  the  stretched  paper  may  absorb  enough 
moisture  so  that  it  will  again  wrinkle,  especially  in  the  corners 
where  it  may  not  have  been  sufficiently  moistened  when 
stretched.  In  this  case,  with  a  knife  make  cuts  along  and 
outside  of  the  cutting  lines  of  the  paper  in  the  neighborhood  of 
the  wrinkle.  Cut  enough  so  that  the  paper  will  lie  flat  and  the 
T  square  will  pass  over  the  wrinkled  spot  with  no  trouble. 
The  shrinkage  of  the  drawing-boards  often  causes  these 
wrinkles,  and  it  is  often  necessary  to  cut  lines  along  the  whole 
of  the  top  and  bottom  of  the  paper  and  a  short  distance  up  the 
sides  before  the  T  square  will  lie  flat.  Cut  only  a  small 
amount  on  the  sides  and  as  much  on  top  and  bottom  as  is 
necessary.  Generally  it  is  necessary  to  cut  clear  across  top 
and  bottom.  The  paper  is  still  stretched  by  being  held  at  the 
sides,  and  good  work  may  still  be  done  on  it.  Never  put  a 
thumb-tack  in  the  paper  where  it  has  been  cut  as  stated  above. 
Let  it  lie  flat. 

Profile  Drawings. — These  drawings  are  those  of  figures  on 
a  plane,  and  are  principally  used  in  Plane  Descriptive  Geometry 
and  for  the  purpose  of  learning  how  to  use  the  various  instru- 
ments. The  first  two  drawings  are  Profile  Drawings. 

General  Arrangement. — In  making  drawings  of  compli- 
cated arrangements  of  mechanism,  as  a  ship,  machinery,  pipe- 
lines, turrets,  etc.,  a  general  plan  is  first  made  from  the  main 
ideas  of  the  results  to  be  accomplished.  In  the  case  of  the 
ship,  the  general  plan  shows  the  location  of  the  many  impor- 
tant parts  of  the  structure,  and  is  made  in  a  very  general  way 
with  no  attempt  at  detail.  In  the  case  of  a  complicated  engine, 
the  general  plan  called  "  General  Arrangement  of  Machinery  " 
shows  how  the  machinery  is  to  be  assembled  after  the  indi- 


GENERAL   DIRECTIONS.  35 

vidual  parts  are  completed.  The  same  applies  to  the  turret, 
the  positions  of  the  various  mechanisms,  guns,  rammers, 
elevating-devices,  etc.,  being  shown. 

In  these  general  arrangements  only  the  principal  dimen- 
sions are  given,  so  that,  when  each  portion  is  completed,  it 
may  be  secured  in  its  proper  place.  There  is  no  detail,  though 
the  general  appearance  of  the  details  may  be  drawn. 

Working  Drawings. — After  the  general  arrangement  is 
completed,  working  drawings  are  made  of  the  various  portions 
that  make  up  the  complete  mechanism.  Each  portion  is 
drawn  in  the  minutest  detail,  so  that  the  many  workmen  em- 
ployed in  manufacturing  the  various  articles  may  be  able  clearly 
to  understand  how  each  one  is  to  be  manufactured.  As  many 
views  as  are  necessary  to  a  thorough  understanding  of  the 
subject  must  be  made.  It  is  not  sufficient  to  make  the  views 
to  an  exact  size  on  an  exact  scale ;  dimensions  must  be  placed 
on  the  working  drawings  so  that  it  will  not  be  necessary  for 
the  workmen  to  use  a  rule  in  order  to  determine  the  size  of  any 
important  part  or  minor  detail  of  the  piece  worked  upon. 
These  dimensions  must  be  clearly  placed  on  the  drawing. 

Working  drawings  are  sometimes  made  on  white  paper  in 
pencil,  inked  and  finished,  and  then  varnished  and  sent 
directly  to  the  shops.  Sometimes  they  are  finished  as  before 
and  are  then  traced  and  blue-printed  and  then  sent  to  the 
shops.  They  are  traced  by  placing  over  them  a  transparent 
paper  or  cloth  and  a  copy  made.  These  drawings  on  trans- 
parent cloth  or  paper  are  then  treated  as  films  used  in  cameras 
and  prints  are  made.  Generally  blue-prints  are  used.  The 
great  advantage  of  tracing  and  blue-printing  is  that  as  many 
prints  as  desired  may  be  made. 

The  business  method  at  present  is  to  make  the  drawing  in 
pencil  on  white  or  on  cheaper  brown  drawing-paper  and  then 
to  trace  directly  from  the  pencil-work,  the  tracing  being 
the  only  finished  drawing  made.  This  tracing  is  then  the 
"  original  "  and  is  carefully  preserved,  while  the  pencil  drawing 


3  MECHANICAL   DRAWING. 

is  destroyed.     In  this  case  the  pencilled  drawing  is  completed: 
dimensions,  legend,  etc.,  but  no  shade  lines  or  hatching. 

Before  giving  the  method  of  procedure  in  making  drawings, 
certain  methods  used  will  be  explained.  These  should  be 
referred  to  when  drawings  are  being  made  as  the  need  of  using 
each  one  appears. 

Views. — In  general,  mechanical  drawing  of  the  practical 
kind  requires  only  orthographic  projections — those  where  the 
rays  of  light  are  all  parallel  for  each  view  of  an  object  and 
where  all  lines  are  represented  full  size  or  to  scale.  In  order 
to  show  an  object  clearly  by  mechanical  drawing,  it  may  be 
necessary  to  make  several  views  of  the  object.  These  views 
are  taken  from  positions  at  right  angles  with  each  other.  The 
first  view  to  be  considered  is  the  Plan.  The  object  may  be 
supposed  to  rest  on  the  drawing-board  or  the  ground,  and  the 
draftsman  is  directly  over  each  point  of  the  object  and  en- 
deavors to  represent  the  object  on  paper  as  it  appears  to  him 
from  his  point  of  view.  Measurements  are  taken  and  the 
object  drawn. 

The  next  view  to  consider  is  the  Front  Elevation.  Leav- 
ing the  object  in  its  position,  the  draftsman  moves  to  one  side 
— generally  the  longest  side — and  is  supposed  to  have  his  eye 
for  each  point  of  the  object  in  a  direction  at  right  angles  to  the 
vertical  and  at  right  angles  to  the  central  plane  of  the  Plan 
view.  He  takes  measurements  from  this  point  of  view  and 
draws  the  object  as  it  appears  to  him. 

The  next  view  is  the  Side  or  End  Elevation.  The  object 
remains  as  before  and  the  draftsman  moves  to  one  end — 
generally  to  the  end  on  the  right  of  his  position  for  the  Front 
Elevation — where,  for  each  point  of  the  object,  his  eye  is  sup- 
posed to  be  in  a  direction  at  right  angles  to  the  central  planes 
of  both  the  Plan  and  the  Front  Elevation.  He  takes  measure- 
ments and  draws  the  object  as  it  appears  from  that  point  of  view. 

These  three  are  the  views  generally  taken ;  in  a  few  cases, 
where  the  object  has  a  complicated  structure,  it  may  be  neces- 


GENERAL   DIRECTIONS. 


37 


sary  to  draw  the  other  End  or  Front  Elevation  and  occasionally 
it  may  be  necessary  to  draw  a  Bottom  View,  as  though  the 
draftsman  were  underneath.  In  that  case  the  object  is  turned 
bottom  up  while  the  dimensions  are  taken,  if  possible. 


Another  way  to  look  at  this  method  of  making  the  different 
views  is  to  first  consider  the  object  resting  as  before  and  draw 
the  Plan.  Then  consider  that  the  object  is  tipped  over 
through  an  angle  of  90°,  the  top  moving  away  from  the  drafts- 
man as  he  stands  in  position  for  drawing  the  Front  Elevation ; 
by  placing  the  eye  directly  over  the  object  in  the  new  position, 
a  drawing  maybe  made  as  for  the  original  Plan.  For  the  end 
view,  the  object  in  its  position  for  Front  Elevation  may  be 
considered  to  be  tipped  over  through  an  angle  of  90°,  the  top 
moving  to  the  left  of  the  draftsman  as  he  stands  in  position  for 
drawing  the  Front  Elevation ;  by  placing  the  eye  directly  over 
the  object  in  the  new  position  a  drawing  may  be  made  as  for 
the  original  Plan. 

The  other  Side  Elevation,  Front  Elevation,  and  Bottom 
View  may  be  considered  in  the  same  manner,  by  revolving"  the 
object  as  required  in  each  case. 


FIG.  16. 


38  MECHANICAL   DRAWING. 

Another  method. — Imagine  the  object  partly  surrounded 
by  three  transparent  planes  A ,  B,  C,  and  that  on  each  plane  is 
projected  an  outline  of  the  object,  bringing  the  Plan  or  top 
view  on  plane  A ,  the  Front  Elevation  on  plane  B,  and  the  Side 
Elevation  on  plane  C.  Flatten  out  these  planes  by  separating 
two  of  them  along  the  edge  Im  and  moving  them  in  the  direc- 
tions shown  by  the  arrows,  and  the  views  will  be  arranged  as 
shown  to  the  right. 


Besides  these  views  it  may  often  be  necessary  to  make 
other  special  views  of  the  object,  or  special  sections,  or  special 
enlarged  views  of  minor  parts  of  the  mechanism.  These  may 
be  placed  on  the  board  according  to  judgment;  as  a  rule, 
however,  it  is  well  to  place  these  lesser  views  as  near  their 
position  on  the  larger  views  as  possible. 

The  views  need  not  be  drawn  in  the  order  given,  as  it  may 
very  much  simplify  the  work  if  the  Front  or  Side  Elevation  is 
drawn  first. 

The  method  of  arranging  the  views  is  as  follows : 

Plan. 

Side  Elevation.      Front  Elevation.      Side  Elevation. 
Bottom  View. 

As  the  Bottom  View  is  seldom  required  and  one  of  the 
Side  Elevations  generally  suffices,  the  ordinary  arrangement 
is  as  follows: 

Plan. 

Front  Elevation.  Side  Elevation. 

Projections. — In  describing  the  method  of  considering  the 
object  as  revolved  through  angles  of  90°,  it  will  be  noted  that 
each  point  of  the  object  moves  in  a  plane  and  keeps  its  same 
relative  position  from  any  edge  that  it  had  originally. 

Consider  the  Plan  as  drawn  and  place  the  object  over  the 
drawing.  It  will  of  course  exactly  cover  the  lines  drawn. 


GENERAL   DIRECTIONS. 


39 


Revolve  the  object  for  the  Front  Elevation — that  is,  so  that 
the  top  moves  up  the  drawing-board — and  it  will  rest  on  its 
side  above  the  Plan.  Draw  the  object  directly  down  the  board 
until  below  the  Plan  with  any  desired  amount  of  space  between. 
Measure  the  object  as  it  appears  from  a  point  directly  over  it ; 
remove  the  object  and  make  the  drawing.  It  will  appear  as 


FIG.  17. 

shown  in  the  Front  Elevation.  In  this  case  the  narrow  side 
is  taken  for  the  Front  Elevation.  Note  that  each  point  of  the 
object  described  a  line  in  a  vertical  plane  or  one  up  and  down 
the  board,  as  it  was  revolved ;  and  that  the  point  was  drawn 
along,  after  being  revolved,  in  a  vertical  direction  or  along  the 
drawing-board,  so  that  the  point  always  remained  in  the  same 
plane ;  and  the  plane  was  certain  to  contain  the  point  no  matter 
at  what  part  of  its  revolution  or  movement  vertically.  Then 
draw  dotted  lines  vertically  from  any  points,  as  a,  b,  c,  d,  to 
represent  these  planes,  and  the  points  will  at  all  parts  of  the 
movement  be  somewhere  in  the  planes  represented  by  these 
lines. 

In  the  same  manner  take  the  object  as  resting  on  the  Front 
Elevation  and  revolve  it  to  the  left  and  then  draw  it  along  the 


4°  MECHANICAL   DRAWING. 

paper  to  a  convenient  distance  to  the  right.  Again,  these 
points,  a,  b,  c,  d,  etc.,  will  revolve  in  a  plane,  and  a  horizontal 
line  will  represent  the  plane  in  which  they  move.  As  they 
are  all  in  the  same  plane,  one  dotted  line  represents  the  one 
plane  in  which  they  all  lie.  The  point  which  was  revolved  to 
a  now  falls  at  a" ;  b,  which  was  projected  to  b\  now  falls  at 
b"\  cy  at  c  and  c"  \  d,  at  d'  and  d" ,  etc.  ;  b"  and  d"  fall  at 
the  same  point;  also  c"  and  /'. 

These  are  called  the  projections  of  the  point.  There  are 
many  methods  of  describing  how  to  make  projections,  but  this 
method  explains  how  they  are  used  in  practice  on  the  drawing- 
board. 

Another  method  of  projecting  the  points  from  the  Plan  to 
the  Side  Elevation  is  shown  in  Fig.  17.  After  the  Front 
Elevation  has  been  drawn  by  projecting  from  the  Plan  as  far 
as  possible  and  finishing  by  putting  in  the  other  lines  as 
measured,  the  line  kl  is  taken,  at  any  convenient  distance  from 
the  Front  Elevation,  as  the  side  line  for  the  Side  Elevation. 
Extend  the  line  kl  upwards  and  project  on  this  line  the  points 
of  the  Plan  that  are  needed  in  order  to  draw  the  Side  Elevation. 
On  k  as  a  center,  swing  these  points  down  to  the  line  km  and 
project  them  from  this  line  to  the  Side  Elevation. 

This  method  is  more  of  a  Descriptive  Geometry  one  than 
a  drafting-room  method  (though  it  is  sometimes  necessary 
there),  and  should  not  be  followed  as  a  rule. 

Distances  are  seldom  measured  more  than  once  on  a  draw- 
ing if  they  can  be  readily  projected. 

Lines. — There  are  three  kinds  used  in  Mechanical  Draw- 
ing; full,  broken,  and  dotted.  See  "Lines  to  be  used  on 
Drawings,"  at  end  of  book. 

The  full  line  is  a  continuous  line.  The  full  line  in  black 
ink  is  used  to  show  any  edge  or  boundary  of  a  surface  when 
the  edge  is  in  sight  from  the  point  of  view  from  which  the 
drawing  is  made.  When  red  ink  is  used,  center  lines  are 
drawn  as  full  lines. 


GENERAL    DIRECTIONS.  41 

The  broken  line  is  one  composed  of  short  or  long  dashes 
with  spaces  between.  The  spaces  should  be  about  one-eighth 
the  length  of  the  dashes.  For  ordinary  work  in  black  ink  the 
dashes  are  about  one-eighth  of  an  inch  long  and  the  spaces 
about  one  sixty-fourth  of  an  inch  in  length.  These  lines  are 
as  heavy  as  the  full  lines  of  the  drawing,  as  they  are  equally 
important,  but  are  never  made  as  heavy  as  shade  lines.  The 
broken  lines  in  black  ink  are  used  to  show  any  edge  or 
boundary  of  a  surface  when  the  edge  is  concealed  from  view. 

When  two  broken  lines  are  parallel  and  close  together, 
break  joints  with  dashes  and  spaces. 

The  broken  lines  are  also  always  used  for  dimension  exten- 
sion lines  and  for  dimension  lines.  The  lengths  of  the  dashes  and 
spaces  vary  in  this  case,  as  explained  under  "  Dimension  Lines." 

The  dotted  lines  are  occasionally  used  for  the  projection  of 
points  from  one  view  to  another.  They  are  seldom  used 
except  for  the  first  drawings  and  when  a.a  exceptionally  diffi- 
cult intersection  is  made. 

The  dotted  line  is  a  seres  of  the  shortest  dashes  that  can 
be  made,  the  spaces  between  being  fully  as  great  as  the  length 
of  the  dashes,  so  that  the  effect  is  that  of  a  series  of  dots. 
These  dotted  lines  are  always  fine  lines,  as  they  are  subordinate 
lines. 

Broken  and  dotted  lines  are  never  shaded. 

Center  Lines. — All  drawings  of  objects  are  made  from 
center  lines.  These  are  the  first  lines  drawn  in  sketching  and 
in  work  on  the  drawing-board.  When  an  object  is  to  be 
sketched  or  drawn,  it  is  examined  and  the  necessary  views 
decided  upon.  Next  determine  the  positions  of  the  center  lines 
of  the  object.  These  lines  are  as  a  rule  imaginary  and  pass 
through  the  center  of  figure  of  the  body  in  the  three  directions 
at  right  angles  to  each  other,  as  must  be  the  case  from  the 
three  views  generally  drawn.  If  the  body  is  uniform  about 
these  centers,  as  a  cube,  there  is  no  difficulty  in  determining 
the  center  lines;  if  it  is  a  cylindrical  body,  there  is  again  little 


42  MECHANICAL   DRAWING. 

difficulty  in  placing  the  center  lines ;  and  so  with  any  body  of 
revolution.  In  most  bodies,  however,  there  is  some  system 
so  that  the  middle  of  the  width  of  one  side  may  be  taken  as  a 
starting-point  in  deciding  on  one  center  line,  and  the  others 
are  arranged  to  the  best  advantage.  In  the  case  of  a  cylindrical 
body,  measure  the  diameter  with  the  calipers  and  the  center 
line  will  be  half-way. 

After  the  center  lines  are  decided  upon,  measurements  are 
made  with  regard  to  them  and  the  sketch  or  drawing  con- 
structed from  them  after  they  are  drawn  in.  The  cylindrical 
part  is  measured  from  the  center  line,  the  radius  laid  off  either 
way.  Distances  parallel  to  the  center  line  are  measured  along 
that  line  and  vertical  lines  are  drawn  through  the  points 
marked.  Then  the  distances  from  the  center  on  these  vertical 
lines  are  measured  and  laid  off  and  the  positions  of  the  points 
in  that  view  are  established.  Each  point  is  in  this  way 
established  in  one  view  and  then  is  projected  to  another  view, 
if  possible,  so  that  the  least  number  of  measurements  may  be 
made. 

The  positions  of  the  views  are  given  under  the  neading 
"Views."  Next  measure  the  extreme  or  "  over-all  dimen- 
sions "  of  the  object  and  decide  on  the  scale  to  be  used  and 
calculate  as  to  where  the  center  lines  of  the  various  views  must 
be  placed.  This  requires  considerable  care  in  order  that  the 
views  may  all  be  placed  on  the  drawing-board  without  inter- 
fering with  each  other  and  so  that  the  points  may  be  properly 
projected  for  the  views.  As  a  rule,  the  positions  of  the  center 
lines  for  the  Plan,  one  of  which  extended  will  be  a  center  line 
for  the  Front  Elevation  as  well,  are  decided  upon  first,  if  a 
Plan  is  to  be  drawn.  After  that  the  positions  of  the  center 
lines  of  the  Front  Elevation,  one  of  which  will  also  be  a  center 
line  for  the  Side  Elevation,  are  decided  upon.  Then  the  other 
or  vertical  center  line  for  the  Side  Elevation  is  decided  upon. 
All  these  center  lines  should  be  drawn  in  pencil  before  any 
work  is  done  on  the  drawing. 


GENERAL   DIRECTIONS.  43 

These  center  lines  should  be  drawn  with  the  greatest  care 
and  should  be  firm,  clean  lines,  as  measurements  are  made 
along  and  on  either  side  of  them,  and  the  accuracy  of  the  work 
depends  on  the  accuracy  of  the  center  lines. 

Center  lines  are  drawn  for  each  view  of  the  object  repre- 
sented, and  for  centers  of  bolts  or  bolt-holes  and  wherever 
centers  are  used  in  constructing  the  drawings.  They  are  inked 
in  after  the  black-ink  work  is  entirely  completed,  and  are  drawn 
dash-dot  in  black  ink  with  the  lines  extending  beyond  the 
figures  for  a  distance  of  from  J"  to  i",  depending  on  the  size 
of  the  figure.  The  system  of  extending  the  center  lines  until 
they  meet  other  center  lines  and  thus  form  rectangles  is  not 
approved. 

Shade  Lines. — To  give  life  to  a  drawing  and  to  make  it 
apparently  stand  out  from  the  paper,  shade  lines  or  relief 
lines  are  used.  These  distinguish  raised  and  depressed  por- 
tions of  an  object.  They  are  all  of  the  same  width  and  are 
about  four  times  as  wide  as  the  original  lines ;  in  tracings  they 
are  still  wider. 

Shade  lines  are  always  drawn  outside  the  original  lines  of 
the  figure.  The  light  is  supposed  to  fall  on  the  object  in  all 
views  from  the  top  left-hand  (N.  W.)  direction  at  an  angle  of 
45°  from  above;  and,  generally  speaking,  the  heavy  line  marks 
the  dividing  edge  between  light  and  dark  surfaces,  though  it 
often  marks  edges  when  both  surfaces  forming  the  line  are  in 
shadow. 

The  shade  line  begins  and  ends  at  its  full  width  and  does 

not  slope  at  the  ends,  as,     y^  ;  but  is  drawn     \     . 

The  positions  of  these  lines  are  largely  conventional,  but 
certain  general  customs  prevail. 

As  a  rule,  the  right-hand  and  lower  sides  of  the  figures  are 
shaded ;  the  opposite  for  interior  openings. 

In  Fig.  1 8,  A  shows  a  central  raised  portion  and  B  a  de- 
pressed interior  portion. 


44 


MECHANICAL   DRAWING. 


The  question  of  the  lines  to  be  shaded  may  be  studied  by 
considering  which  edges  would  cast  shadows  if  the  object  were 
placed  so  that  the  light  came  from  the  proper  direction. 


FIG.  18. 

Place  a  60°  triangle  on  the  drawing-board  in  position 
against  the  T  square  and  then  remove  the  T  square.  Shadows 
will  be  found  at  a,  b,  and  c.  Place  a  45°  triangle  beside  the 


FIG.  19. 

60°  one  and  shadows  will  be  found  at  b  and  c  only.  As  the 
light  now  shines  along  the  side  a,  there  is  no  shadow,  and 
hence  no  shade  line.  Turn  the  triangles  the  other  way  and 
remove  the  square  and  the  shadows  in  both  will  be  found  at 


FIG.  20. 


d,  e,  and/.      Now  turn  the  triangles  about  centers  and  note 
where  the  shadows  begin  and  end  on  the  different  interior  and 


GENERAL   DIRECTIONS. 


45 


exterior  edges  while  the  turning  slowly  proceeds.  Since  all 
the  rays  of  light  are  considered  parallel  and  all  come  from  the 
N.  W.  and  from  above  at  an  angle  of  45°,  the  shadows  begin 
as  soon  as  the  direct  rays  of  light  fail  to  strike  the  edges. 

The  edges  to  have  shade  lines  may  generally  be  readily 
determined  by  eye,  but  if  an  edge  away  from  the  source  of 
light  is  nearly  in  a  N.  W.  direction,  the  question  of  the  shade 
line  may  be  determined  by  placing  a  45°  triangle  in  position 
on  the  T  square.  If  the  edge  of  the  solid  body  farthest  from 
the  source  of  light  is  beyond  the  45°  point,  so  that  the  light 
does  not  shine  along  that  edge,  a  shade  line  should  be  placed 
on  the  drawing. 

Cylindrical  and  other  curved  surfaces  are  shaded. 

When  circles  are  shaded,  the  method  given  above  of 
determining  the  shaded  portions  by  using  the  45°  triangles  will 
be  followed.  The  shade  lines  begin  at  the  points  where  the 
light  fails  to  strike  the  edges.  These  points  are  determined 
by  the  45°  triangle  placed  on  the  T  square  and  held  just  tan- 
gent to  the  arc ;  but  a  simpler  way  is  to  place  the  triangle  on 
the  T  square  in  the  reversed  position  with  the  diagonal  edge 
at  the  center  of  the  circle 

This  edge  will  be  a  normal  to  the  tangents  at  a  and  b,  and 
marks  may  be  made  there  for  the  ends  of  the  shade  lines. 


FIG.  21. 


For  an  interior,  as  the  inner  line  of  the  hollow  cylinder  in 
Fig.  21,  the  opposite  part  of  the  arc  is  shaded;  the  points 
of  beginning  and  ending  are  found  as  before. 

In  shading  these  circles,  it  is  generally  customary  to  taper 


46  MECHANICAL   DRAWING. 

the  shade  line  to  nothing  at  a  and  b  and  make  it  heaviest  at 
c,  the  point  of  broadest  shadow. 

There  are  several  methods  of  drawing  these  irregular  shade 
lines.  The  best  method  is  as  follows  (see  Fig.  22):  After 
drawing  the  original  circle,  begin  again  near  a,  but  between  a 
and  cy  and  slightly  spring  the  compass  without  changing  the 
set  of  the  instrument,  following  along  a  line  like  the  outer  por- 
tion of  the  line  between  a  and  ^,  through  c.  This  requires  a 
gradual  springing  open  and  a  gradual  closing  of  the  instru- 


FIG.  22.  FIG.  23. 

ment,  and  requires  considerable  practice  before  perfect  work 
may  be  done.  After  the  outer  line  is  drawn,  the  space  between 
the  lines  may  be  filled  in  by  springing  the  instrument  as 
desired,  at  the  same  time  opening  the  pen-points  wider. 
Always  draw  in  the  same  direction,  however,  returning  for 
each  new  sweep  of  line. 

The  heaviest  part  of  the  shade  is  about  four  times  as  heavy 
as  the  original  line,  as  in  the  case  of  the  straight  lines. 

Another  method  of  drawing  shade  lines  of  circles  is  as 
shown  in  Fig.  23. 

Begin  at  the  point  c  near  a  and  draw  a  heavy  shade  line 
(four  times  the  width  of  the  ordinary  line)  to  a  point  d  near  b. 
From  a  to  c  and  from  b  to  d  taper  the  line  by  springing  the 
instrument  as  described  above.  This  method  is  little  used. 

For  irregular  curves  or  for  portions  of  arcs  the  points  of 
beginning  and  ending  of  shade  lines  are  determined,  as  with 


GENERAL    DIRECTIONS. 


47 


straight  lines,  by  the  45°  triangles.  In  this  case,  the  shading 
tapers  from  nothing  to  the  full  width,  as  explained  in  the 
second  method  of  shading  circles. 

Fig.    24  represents  a  fillet,    a  small    arc    of  a 
circle  joining    two    straight    lines.       The    point    of 
beginning    the     shade    is   determined    by    the    45° 
FIG.  24.       triangle  set  at  the  center  of  the  arc,  and  the  shading 
is  gradual  up  to  the  point  of  meeting  the  straight  line. 

Fig.  25  represents  a  curved  surface  like  a  section  of  a  por- 


FIG.  25. 

tion  of  a  cylinder-head.      The  shading  is  shown.      Note  that 
the  shade  lines  cross  the  figure  at  the  45°  points. 

When  surfaces  of  separate  portions  of  the  figures  are  touch- 
ing and  are  at  the  same  level,  no  shade  lines  are  drawn. 


2 

]a 

b 

FIG.  26. 


In  A   and  A',  Fig.  26,  block   I   is  wider   and    lower  than 
block  2.      In  the  top  figure  or  plan  view,  when  looking  down 


48 


MECHANICAL   DRAWING. 


on  the  blocks,  the  sides  a,  c,  and  d  are  shaded  in  accordance 
with  the  general  plan ;  the  line  b  is  shaded  only  where  it  is 
free  from  block  2,  as  its  edge  in  contact  with  block  2  cannot 
cast  a  shadow.  In  the  lower  figure  or  elevation,  when  looking 
at  the  side  of  the  blocks,  a,  c,  and  d  are  shaded  by  the  general 
plan,  and  b  is  shaded  as  it  projects  beyond  the  block  2. 

In  figures  B  and  B'y  where  the  blocks  are  equally  high  and 
wide,  there  is  no  shade  line  at  b  in  either  view,  as  the  edges 
are  on  the  same  level. 

In  figures  C  and  Cf,  block  2  is  lower  and  wider  than 
block  I.  In  the  top  or  plan  view,  when  looking  down  on  the 
blocks,  the  sides  a,  c,  and  d  are  shaded  by  the  general  plan 
and  b  is  shaded  where  block  I  is  higher  than  block  2,  as  it 
may  there  cast  a  shadow ;  but  the  remainder  of  the  line — that 
for  block  2  only — is  not  shaded,  as  the  light  may  strike  that 
edge. 

In  the  lower  view,  or  elevation,  when  looking  at  the  side 
of  the  blocks,  the  lines  a,  c,  and  d  are  shaded  by  the  general 
plan,  and  b  is  shaded  only  where  block  I  is  above  block  2. 

As  seen  above,  in  shading  one  view  of  an  object,  it  is  often 
necessary  to  refer  to  the  other  views. 

The  shade  lines  are  drawn  outside  the  original  lines  so  that 


FIG.  27. 

the    inner    dimensions    may    be    retained    and    measurements 
accurately  taken.      This  method  also  allows  placing  the  arrow- 


GENERAL   DIRECTIONS. 


49 


points  used  for  marking  the  dimensions  so  that  they  just  touch 
the  inner  edges  of  the  figures,  as  in  Fig.  27. 

All  the  shade  lines  should  be  of  the  same  width.  Make  a 
sample  line  on  the  border  of  the  paper  and  often  test  the  set 
•of  the  pen  with  this  sample  line. 

Shade  lines  are  not  shown  in  the  pencil  drawings. 

Dotted  or  broken  lines  are  never  shaded. 

Bolt-heads  are  shaded  in  various  ways,  but  the  best  method 
is  shown  in  Fig.  28.  It  will  be  observed  that  the  general  plan 
is  followed. 


FIG.  28. 


Where  a  bolt,  rod,  rivet,  etc.,  is  represented  in  elevation 
resting  in  a  section,  the  shading  conforms  to  the  method  shown 
in  Fig.  29. 


FIG.  29. 

Shade  a,  keeping  outside  the  head  of  the  rivet. 
Shade  b,  keeping  outside  the  rivet. 
Shade  c,  keeping  outside  the  plate. 
Shade  d,  keeping  outside  the  section. 
Shafts  and  other  Cylindrical  Objects. — In   representing 
these  on  the  drawing-board,  it  is  best  always  to  draw  first  the 


MECHANICAL   DRAWING. 


view  that  shows  the  shaft  as  a  circle.      Measure  off  the  radius 
from  the  center  and  strike  in  the  circle.      For  the  other  views, 


FIG.  30. 

the  straight  lines  may  be  projected  from  the  arcs  and  time  will 
be  saved. 

Sections. — If  an  object  is  cut  through  by  an  imaginary 
plane  in  any  direction,  the  drawing  showing  the  appearance  of 
this  imaginary  cut  is  called  a  section.  (See  models  of  sec- 
tions.) 

The  draftsman  is  supposed  to  be  in  a  position  normal  to 
this  cutting  plane,  and  to  draw  what  appears  from  that  point  of 
view. 

Sections  are  drawn  to  show  clearly  a  hollow  interior  or  to 
clear  up  any  part  of  the  drawing  that  is  not  lucid  from  the 
other  views,  and  considerable  choice  may  be  made  in  the  posi- 
tions of  the  cutting  planes  chosen.  These  are,  however, 
usually  taken  either  vertically  or  horizontally,  though  they  are 
sometimes  taken  in  other  directions;  but  they  are  generally 
perpendicular  to  either  a  vertical  or  horizontal  plane.  Often 
a  vertical  plane  is  passed  through  on  a  radius  on  the  Plan,  and 
the  section  is  swung  around  until  it  coincides  with  the  plane  of 
the  paper,  when  it  is  drawn. 

When  a  section  is  made,  the  drawing  must  show  not  only 
the  part  of  the  object  in  the  plane,  but  everything  beyond  to 
the  end  of  the  figure. 

Those  parts  concealed  by  the  figure  are  drawn  in  broken 
lines.  Sometimes  portions  of  the  object  beyond  the  section 
plane  may  be  omitted  when  the  drawing  would  be  too  compli- 
cated ;  the  main  outlines  are  always  drawn. 

In   making  a  Plan   or  Elevation,   it  is   sometimes  well  to 


GENERAL   DIRECTIONS.  51 

make  part  of  a  view  a  section ;  or  to  remove  a  portion  of  the 
object  to  more  clearly  show  the  interior.  In  this  case,  the  line 
of  demarkation  is  always  a  solid  black  line  made  with  the 
right-line  pen,  and  is  generally  straight.  This  line  is  shaded 
in  accordance  with  the  directions  under  "  Shading." 

If  a  section  is  made  at  any  plane,  a  heavy,  broken  line  is 

drawn  at  that  plane,  and  its  extremities  are  marked  A B, 

C D,  etc.,  and  the  drawing  of  the  section  is  clearly 

marked,  Section  AB,  Section  CD,  etc.;  or,  Section  on  AB\  or, 
Section  on  line  AB. 

The  section  drawn  may  not  follow  a  plane,  but  may  run 
irregularly  across  the  figure;  the  broken  line  will  follow 
the  course  of  the  section,  however,  so  that  its  course  may  be 
clearly  marked. 

Hatching. — In  making  a  drawing  of  a  section,  the  por- 
tions where  the  plane  passes  through  solid  substances  are 
"hatched."  This  consists  in  covering  these  portions  of  the 
surface  with  lines  of  various  kinds,  to  represent  the  fact  that 
solid  substance  is  cut;  and  also  to  represent,  according  to 
accepted  methods,  the  kind  of  substance  that  is  cut  by  the 
plane.  (See  drawing  of  Standard  Hatching  at  end  of  book.) 

Hatching  is  never  drawn  in  pencil ;  in  black  ink  only. 

The  lines  of  hatching  are  of  various  widths  apart,  according 
to  the  size  of  the  surface  to  be  covered.  For  small  surfaces 
the  lines  are  quite  close  together,  as  in  Fig.  31. 


I      \     ^ 

FIG.  31. 

For  larger  surfaces  the  distance  apart  of  the  lines  increases, 
until,  for  a  very  large  surface,  the  lines  may  be  as  in  Fig.  32. 

It  is  also  customary  in  making  sectional  views  of  very  large 
surfaces  to  begin  the  hatching  away  from  the  edges,  as  shown 
in  Fig.  33. 


5  2  -     MECHANICAL    DRA  WING. 

Still  another  custom,  for  reduction  of  the  work  of  hatching 
large  surfaces,  is  shown  in  Fig.  34. 


FIG.  32. 


FIG.  33. 


FIG.  34. 

These  last  two  conventions  are  used  especially  in  drawings 
of  embankments,  etc.  In  machine  drawings  these  methods 
are  seldom  necessary. 

The  lines  for  hatching  are  drawn  with  the  45°  triangle  as 
long  as  that  angle  can  be  used,  the  first  ones  used  being 
always  the  lines  from  S.  W.  to  N.  E.  on  the  board.  When 
two  surfaces  cut  by  the  plane  of  section  join  along  a  line,  one 
of  the  sets  of  lines  for  hatching  must  be  inclined  one  way  45° 
and  the  other  one  the  other  way  45°,  so  as  to  distinguish 


GENERAL   DIRECTIONS. 


53 


the  separate  pieces  readily.  A  third  substance  in  contact  with 
either  of  these  two  must  have  hatched  lines  at  another  angle; 
a  fourth  at  still  a  different  angle,  etc.  After  the  two  45°  lines 
have  been  used,  it  is  customary  to  draw  the  others  that  are 
necessary  with  the  60°  triangle. 

After  the  drawing  is  inked  and  dimensioned,  the  hatching 
is  done.  Set  the  pen  to  make  clear  lines,  not  too  fine ;  decide 
on  the  angle  of  the  lines  and  their  distance  apart ;  with  the  tri- 
angle at  the  correct  angle  begin  at  the  portion  of  the  surface 
to  be  covered  that  will  allow  the  triangle,  as  it  moves  back  for 
the  hatching,  to  sweep  from  end  to  end  of  the  surface;  space 
the  distance  apart  by  eye  and  do  not  try  to  get  a  certain  number 
of  lines  per  inch.  Do  not  attempt  to  have  the  lines  come  out 
even  at  any  point;  the  distance  apart  is  what  is  important; 
cover  the  entire  surface  that  belongs  to  the  same  body  with 
lines  at  the  same  angle  and  the  same  distance  apart. 

Hatching  machines  of  various  kinds  are  a  mistake  for 
beginners.  A  steady  hand  and  a  quick  eye  will  soon  cause 
proficiency,  and  the  training  is  excellent. 

When  two  surfaces  of  about  the  same  size  and  the  same 
material  meet  at  a  line  and  both  are  to  be  hatched,  finish  one 
hatching,  and  draw  the  other  so  that  the  various  lines  meet 
the  first  set  of  lines  at  the  line  of  demarkation,  as  in  Fig.  35. 


FIG.  35. 


FIG.  36. 


Another  method  that  emphasizes  the  line  of  separation  of 
the  surfaces  is  shown  in  Fig.  36. 

When  the  hatching  consists  of  heavy  and  light  lines,  the 
surface  is  hatched  across  with  the  light  lines  as  though  those 
lines  were  the  only  ones  to  be  used.  The  correct  spaces  are 
then  filled  in  solid,  producing  the  heavy  lines. 


54 


MECHANICAL    DRAWING. 


To  fill  in  these  spaces,  draw  a  fairly  heavy  line  on  either 
side  of  the  space  to  be  filled ;  go  over  all  the  spaces  of  any  one 
portion  of  metal  and  allow  these  lines  to  become  dry;  then 
open  the  pen  wider  and  fill  in  the  central  portions.  These 
filling  lines  are  drawn  with  the  R.  L.  pen  guided  by  the  tri- 
angle. Never  fill  in  with  a  writing-pen  or  use  the  R.  L.  pen 
as  a  brush. 

This  method  of  filling  the  spaces  causes  a  loss  of  time,  as 
the  first  lines  drawn  must  be  allowed  to  dry,  but  the  method 
is  a  safe  one.  A  more  rapid  method  and  a  better  one  after 
sufficient  experience  has  been  acquired  is  to  fill  each  of  the 
spaces  at  once  by  drawing  line  after  line  until  the  surface  of 
the  space  is  covered  with  liquid  ink.  The  ink  will  then  dry 
evenly  over  the  entire  surface  of  the  space.  Also,  this  allows 
of  continual  advancement  without  waiting  for  lines  to  dry. 
Caution  is  necessary  to  keep  the  triangle  well  away  from  the 
liquid  lines  of  ink  or  a  bad  blot  will  result. 

Just  as  good  ink-lines  are  required  for  hatching  as  for  the 
other  parts  of  the  drawing.  Do  not  attempt  to  make  the  lines 
of  hatching  too  fine. 

In  doing  hatching,  glance  back  after  drawing  every  ten  lines 


FIG.  37. 

or  so  to  see  that  the  spacing  continues  regular;  if  irregular, 
gradually  change  the  spacing  until  the  exact  amount  is 
obtained. 

In   drawing  sections  where  the  plane  passes  through  the 
center  line  of  a  cylindrical  body,  the   cylinder  is  generally  not 


GENERAL   DIRECTIONS. 


55 


hatched,  but  is  drawn  in  elevation,  resting  in  the  section. 
This  refers  to  shafts,  spindles,  bolts,  rivets,  etc.,  as  in  Fig.  37. 
Fig.  38  shows  a  Plan  and  Elevation  of  a  steam-cylinder. 
The  Plan  is  half  in  section,  the  section  taken  at  the  line  AB 
of  the  Elevation.  The  upper  half  of  the  half-cylinder  is 
removed  and  the  section  drawn,  the  lower  flange  of  the 


FIG.  38. 

cylinder  showing  below  the  section.  Each  bolt-hole  is  drawn, 
and  the  centers  marked,  first  by  the  circular  center  line  and 
also  by  the  short  radial  lines. 

The  elevation  of  the  cylinder  is  also  half  in  section,  the 
section  made  at  the  plane  CD  in  the  Plan.  In  this  case  the 
front  half  of  the  half-cylinder  is  removed  and  the  section 
drawn.  The  top  and  bottom  lines  of  the  flanges  and  the 
opening  at  the  bottom  are  carried  across  to  the  center  line. 
The  lower  line  of  the  upper  flange  in  the  section  is  a  broken 
line,  as  this  rim  of  the  flange  is  concealed  behind  the  section. 


56  MECHANICAL  DRAWING. 

The  line  at  the  right  of  the  opening  in  the  bottom  of'the 
cylinder  is  a  lull  line,  as  the  edge  of  the  opening  is  in  view 
though  the  curve  drops  away  from  the  plane  of  the  section. 

Besides  the  main  center  lines  for  both  figures  there  are 
drawn  in  the  Plan  the  circular  center  line  and  the  short  radial 
dashes  for  the  bolt-holes,  and  in  the  Elevation  the  short  center 
lines  for  the  bolt-holes.  In  the  Elevation  only  the  bolt-hole 
at  the  diameter  is  dotted  in  the  outside  view,  and  drawn  full  in 
the  section.  The  other  bolt-holes  are  shown  sufficiently  in 
the  Plan.  The  hole  in  the  bottom  of  the  cylinder  is  shown  in 
the  Elevation,  one  edge  drawn  full  in  the  section,  and  the  other 
a  broken  line.  The  lines  in  both  Plan  and  Elevation  separat- 
ing the  section  from  the  other  view  are  drawn  full  black  lines ; 
their  extensions,  the  center  lines  extended,  are  drawn  in  as 
usual.  These  black  division  lines  are  shade  lines  as  explained 
under  the  heading  "Shade  Lines." 

Breaks. — Breaks  are  used  in  drawings  to  represent  that  a 
shaft,  rod,  etc.,  is  broken  off.  This  is  done  when  there  is  not 
enough  space  on  the  paper  to  draw  in  full  length  any  portion 
of  the  mechanism,  or  when  it  is  undesirable  and  unnecessary 
to  use  the  space  required  for  the  purpose.  These  breaks  are 
also  used  to  show  the  shape  of  the  cross-section  and  the  kind 
of  material  of  which  it  is  composed.  They  are  complete  in  one 
'view  and  have  no  reference  to  any  other  view. 


FIG.  39. 

The  irregular  lines  of  fracture  are  made  in  black  ink  and 
are  drawn  best  with  the  R.  L.  pen  held  carefully  and  twisted 
in  the  fingers,  so  as  to  keep  the  nibs  always  parallel  with  the 
line  of  direction  of  the  movement.  One  of  these  lines  is  a 
shade  line  throughout;  the  other  a  light  line.  This  adds  much 
to  the  effect. 


GENERAL   DIRECTIONS. 


57 


The  rod  must  always  be  broken  as  shown,  so  that  a  piece 
is  lost  from  the  central  portion  and  the  ends  left  intact.  In 
this  way  the  total  length  or  ' '  over-all  dimension  ' '  may  be 
given. 


-/&"- 

FIG.  40. 

A  variation  is  sometimes  made  in  the  method  of  making 
the  break,  as  shown  in  Fig.  40.  This  shows  the  material,  the 
hatching  being  done  in  accordance  with  the  ' '  Standard 
Hatching. " 

Often  breaks  are  made  of  small  portions  of  a  piece  of 
mechanism  in  company  with  a  portion  of  a  section,  as  shown 
in  Fig.  41. 


FIG.  41. 

In  order  to  show  the  kinds  of  metals,  and  to  make  more 
clear  the  interior  of  the  mechanism,  the  irregular  break  is 
made.  It  is  considered  that  this  break  extends  inward  to  the 
center  line  and  that  the  top  half  is  removed.  This  irregular 
break  is  drawn  as  before  with  a  R.  L.  pen  used  carefully. 

Dimension  Lines.  Dimension  Extension  Lines. — Besides 
drawing  the  views  of  an  object  to  correct  size  or  to  a  certain 
scale,  the  dimensions  of  all  parts  of  the  object  must  be  clearly 
placed  on  some  of  the  different  views,  so  that  whoever  may 


MECHANICAL    DRAWING. 


have  occasion  to  use  the  drawing  will  not  be  obliged  to  measure 
any  dimension. 

Auxiliary  lines  are  used  for  these  dimensions.  They  are 
light,  broken  lines  in  black  ink  and  are  drawn  after  the  center 
lines  are  completed.  The  lengths  of  the  dashes  vary  with  the 
lengths  of  the  lines. 

When  the  dimension  between  two  points  is  to  be  given, 
a  black  broken  line  is  drawn  from  one  point  to  the  other, 
leaving  a  break  near  the  center  for  placing  the  dimension. 
This  line  is  drawn  directly  to  the  points  and  terminates  at 
these  points.  The  dimension  is  placed  in  the  space  left,  and 
at  the  ends  of  the  line  are  placed  arrow-points,  the  points  of 
the  arrows  exactly  at  the  extremities  between  which  the 
dimension  is  taken.  See  Fig.  42. 


^T 

V    I 


FIG.  42. 

Frequently  dimensions  are  given  directly  on  the  views  of 
the  object;  but  when  this  method  crowds  the  drawing,  the 
dimensions  are  placed  beyond  the  outlines,  and  the  distance 
to  be  marked  is  carried  out  from  the  outlines  by  dimension 
extension  lines,  as  in  Fig.  43. 


FIG.  43. 


The  position  of  the  dimension  lines  is  a  matter  of  judgment, 
but  the  greatest  care  must  be  exercised  not  to  complicate  the 


GENERAL   DIRECTIONS. 


59 


drawing  and  not  to  repeat  the  dimensions  on  the  different 
views  unless  this  may  make  a  complicated  drawing  easier  to 
follow. 

Where  two  views  are  beside  each  other,  corresponding 
points  are  often  connected  by  dimension  extension  lines  and 
the  dimension  lines  drawn  between  these,  as  in  Fig.  44. 


FIG.  44. 

When  dimension  lines  are  outside  of  the  views,  these  lines 
are  placed  at  least  J"  away  from  the  outlines  of  the  figures. 

Center  lines  are  never  used  for  dimension  lines,  and  the 
figures  for  the  dimensions  are  not  made  over  the  center  lines. 
The  center  lines  are  left  as  clear  as  possible. 

If  it  can  be  arranged  without  too  much  difficulty,  dimen- 
sions are  not  placed  on  hatched  portions  of  the  drawing ;  but, 
if  it  is  necessary  to  do  this,  leave  irregular  spaces  in  the  hatch- 
ing so  that  the  dimensions  may  be  placed  at  these  points. 

Group  dimensions  that  are  for  portions  of  the  drawings  that 
are  alike;  that  is,  place  them  near  together. 

4  *  Over-all  dimensions  ' '  should  always  be  given  for  con- 
venience in  getting  out  material  for  work.  This  means  the 
dimensions  of  the  greatest  limits  of  the  object  in  the  directions 


45. 


of  the  three  center  lines  at  right  angles.     These  are  generally 

outside   of  the   figures   and   should   be   beyond   all  the   other 

dimensions  that  are  outside  the  figures,  as  in  Figs.  43  and  45. 

The  figures  for  the  dimensions  are  placed  so  as  to  be  read  from 


6o 


MECHANICAL   DRAWING. 


the  bottom  or  right-hand  side  of  the  drawing-board.  They  are 
placed  so  that  the  middles  of  the  figures  and  the  horizontal 
line  of  the  fractions  are  in  line  with  the  dimension  line ;  and  the 
figures  are  at  right  angles  to  the  line.  As  the  dimension  lines 
are  drawn  before  the  figures  are  made,  spaces  must  be  left 
while  drawing  the  dimension  lines.  This  requires  especial 
care  in  dimensioning  diameters  of  circles,  as  in  Fig.  46. 
i 


FIG.  46. 


FIG.  47. 


All  the  dimension  lines  are  in  the  two  quadrants,  as  shown. 

Diameters,  not  radii,  are  dimensioned  where  possible.  If 
radii  must  be  dimensioned,  place  the  arrow-heads  at  both 
center  and  circumference,  as  in  Fig.  47. 

Dimension  extension  lines  are  broken  lines  made  with 
black  ink  and  extend  a  short  distance  beyond  the  points  where 
the  dimension  arrows  are  placed.  See  sketches  43  and  45. 

The  dimension  and  dimension  extension  lines  are  made 
with  dashes  from  -J-"  to  i"  long,  depending  on  the  lengths 
of  the  lines.  The  spaces  between  the  dashes  vary  from  -fa" 
to  TST".  These  lines  are  never  heavy  lines. 

Arrow-points  are  drawn  in  black  ink  with  a  fine  writing- 
pen — not  with  the  R.  L.  pen — and  the  points  of  the  arrows 
touch  the  lines  between  which  the  dimension  is  to  be  given 
The  diverging  lines  of  the  arrow-heads  make  an  angle  of  about 
60°  with  each  other.  These  diverging  lines  are  light,  clean 
lines  from  •&"  to  |"  long. 


GENERAL   DIRECTIONS.  6 1 

When  the  distances  are  small,  these  arrow-heads  are  placed 
on  the  outsides  of  the  lines,  pointing  towards  each  other,  and 
the  dimension  is  either  placed  between  the  points  or  is  carried 
to  one  side  with  an  arrow  pointing  towards  it  from  the  space 
to  be  measured.  See  Fig.  43.  Dimensions  so  carried  away 
are  placed  so  as  to  be  read  from  the  same  direction  as  if  in 
their  correct  positions. 

The  figures  for  marking  the  dimensions  are  made  in  black 
ink  with  a  writing-pen  that  is  not  too  fine.  They  are  made 
clear  and  prominent.  The  shorter  dimensions  must  have  as 
prominent  figures  as  the  large  ones.  These  figures  are  J" 
high  and  stand  at  right  angles  to  the  dimension  lines.  When 
fractions  are  used,  the  line  separating  the  numerator  and 
denominator  is  horizontal,  as  J",  not  3/4 ".  When  mixed 
numbers  are  used,  the  inch  sign  is  placed  after  the  fraction,  as 
2f",  not  2"j. 

When  dimensions  are  given  in  decimals,  the  inch  sign  (") 
is  placed  over  the  zero  mark;  as,  2'.'375,  not  2.375". 

Up  to  and  inclusive  of  24",  dimensions  are  given  in  inches ; 
beyond  24",  the  dimensions  are  given  in  feet  and  inches.  For 
feet  use  ' '  ft.  "  or  « '  feet, ' '  instead  of  the  character  ' ;  as,  2  ft.  6". 

Dimensions  are  given  in  feet,  inches,  and  fractions  of 
inches.  The  fractions  of  inches  used  are  halves,  quarters, 
eighths,  sixteenths,  thirty-seconds,  and  occasionally  sixty- 
fourths.  Fractions  are  always  reduced  to  their  lowest  terms. 
The  total  height  of  the  fraction  is  about  J". 

The  diameters  of  cylinders  and  strokes  of  engines  are  given 
in  inches.  These  are  practically  the  only  exceptions  to  the 
above. 

In  locating  bolts  or  holes,  if  they  are  uniform  on  both  sides 
of  the  center  line,  draw  a  circular  center  line  through  the 
centers  and  give  the  diameter  of  this  "bolt  circle."  This  gives 
the  distance  between  the  centers  of  opposite  bolt-holes  and 
thus  the  radius  of  the  bolt  circle.  Mark  the  center  of  each 
bolt-hole  with  a  short  radial  line. 

If  they  are   not  uniform,  give  the  distance  from  the  center 


62  MECHANICAL   DRAWING. 

line  to  the  center  of  the  bolts.  Occasionally  it  is  necessary  to 
give  the  distance  between  the  center  of  the  bolt  or  hole  and 
the  nearest  edge  of  the  object;  but,  in  general,  distances 
should  be  given  from  the  center  lines.  See  Fig.  48. 


FIG.  48. 

The  number  of  bolt-holes  defines  the  angular  distance  apart. 

On  the  drawing-board  do  not  draw  the  dimension  exten- 
sion lines  and  dimension  lines  in  pencil,  and  do  not  put  down 
the  dimensions  in  pencil  unless  a  tracing  is  to  be  made  from 
the  pencilled  work.  This  is  all  done  in  ink  after  the  drawing 
is  completed. 

On  the  drawing-board  draw  first  the  dimension  lines  and 
then  the  arrows;  this  is  reversed  in  sketching. 

Threads. — The  screw-thread  cut  on  a  bolt  is  for  the  pur- 
pose of  allowing  the  bolt  to  advance  in  the  hole  as  it  is  turned 
around.  As  the  bolt  turns  around  once  it  advances  a  certain 
distance,  called  the  ' '  pitch  ' '  of  the  thread.  The  nut  that 
may  turn  on  the  bolt  has  a  thread  cut  on  the  inside  with  the 
same  pitch  as  the  thread  on  the  outside  of  the  bolt.  The 
thread  cut  on  the  bolt  is  called  a  "  male  "  thread,  and  that  in 
the  nut  a  "female  "  thread. 

If  we  follow  the  top  of  an  ordinary  screw-thread  around  the 
bolt,  we  find  that  for  a  complete  revolution  we  have  advanced 
one  thread.  Hold  the.  bolt  in  a  vertical  position  and  the  front 
elevation  of  the  bolt  shows  that  the  view  of  the  path  of  the 
point  we  followed  is  a  curve.  This  curve  slopes  upward  from 
left  to  right  and  then  passes  behind  the  bolt  and  slopes  upward 
from  right  to  left;  it  reappears  at  the  top  of  the  next  thread. 


GENERAL   DIRECTIONS.  03 

Thus  we  have  advanced  one  pitch.  In  half  the  revolution  one 
half  pitch  was  advanced.  The  same  happens  if  we  follow  the 
path  of  the  bottom  of  the  thread. 

To  represent  the  threads  on  the  drawing-board,  draw  the 
center  line  and  draw  parallel  to  it  lines  for  the  outside  diameter 
of  the  bolt. 


4'r 


FIG.  49. 

Lay  off  on  the  left  side  the  pitch  lengths  ab,  be,  cd,  etc., 
and  the  half-pitch  lengths  at  I,  2,  3,  etc.  Draw  horizontal 
lines  through  these  points.  Then  the  top  of  one  of  the  threads 
will  be  represented  by  the  curved  line  from  a  to  a ',  as  the  dis- 
tance travelled  longitudinally  for  one  half-revolution  will  be  one 
half-pitch.  The  other  half  of  the  revolution  will  cause  the  top 
of  the  thread  to  travel  behind  the  bolt  in  a  line  represented  by 
the  dotted  line  a'b.  The  other  tops  of  the  threads  will  be 
parallel  to  these  two  lines,  as  the  same  cycle  is  repeated 
farther  along  the  bolt. 

The  thread  represented  is  called  a  triangular  thread,  and 
the  standard  angle  for  the  sides  of  the  thread  is  60°.  From 


64 


MECHANICAL   DRAWING. 


the  points  a  and  b  draw  60°  lines  to  meet  on  the  line  of  half- 
pitch  at  e.  This,  then,  is  the  position  of  the  beginning  of  the 
root  of  the  thread.  The  root  will  advance  to  e'  in  one  half- 
revolution  and  the  moving  point  will  follow  the  curved  line  ee' . 
During  the  other  half-revolution  this  point  will  follow  the 
curved  line  e'f  behind  the  bolt.  These  lines,  aa'b  and  ee'f, 
represent,  then,  the  form  of  one  thread  for  one  revolution.  As 
the  other  threads  are  exactly  the  same,  they  are  simply  copies 
of  this  first  one. 

The  curves  made  are  readily  found,  as  they  are  helices, 
and  for  every  portion  of  a  revolution  an  equal  portion  of  the 
total  pitch  is  passed  over  longitudinally. 

It  is  customary  to  show  the  threads  as  shown  in  Fig.  50. 
The  rest  is  shaded  according  to  the  general  plan. 

In  making  drawings,  these  lines  are  seldom  drawn  as 
curves.  They  are  so  near  straight  lines  that  they  are  usually 
represented  as  straight.  Fig.  50  shows  the  appearance  of  the 


FIG.  50. 

threads  as  drawn  when  threads  are  represented  at  all. 

The  straight  lines  simply  replace  the  curved  ones,  and  the 
broken  lines  are  not  drawn. 

To  still  further  simplify  the  representation  of  threads  the 
portion  to  be  threaded  is  shown  as  in  Fig.  5  I . 

The  finer  lines,  I  i,  22,  etc.,  represent  the  tops,  and  the 
heavy  lines  the  bottoms,  of  the  threads.  The  distance  apart 


GENERAL   DIRECTIONS,  65 

of  the  lines  is  not  measured,  but  is  spaced  by  eye  as  in  hatch- 
ing. This  distance  varies  for  different  diameters,  being  smaller 
for  small  bolts  to  represent  approximately  the  number  of 
threads  per  inch  of  length. 

The  finer  lines  are  drawn  first.  In  order  that  the  heavy 
lines  may  begin  and  end  uniformly,  draw  fine  pencil-lines  on 
either  side  and  equally  distant  from  the  side  lines  of  the  bolts, 
as  ab,  cd.  Draw  the  heavy  lines  with  these  lines  for  guides 
for  the  beginning  and  ending,  and  place  them  by  eye  in  the 
middle  between  the  light  lines. 

To  still  further  simplify  the  representation,  sometimes  the 
heavy  lines  are  omitted  entirely,  but  this  is  not  customary 
except  for  very  small  bolts. 

To  find  accurately  the  angle  at  which  to  draw  these  repre- 
sentative lines  it  is  first  necessary  to  know  the  number  of 
threads  to  the  inch. 

If  the  drawing  is  made  from  a  model,  lay  a  rule  along  the 
top  of  the  thread  so  that  one  ridge  corresponds  with  any  inch- 
mark  of  the  rule.  Count  the  number  of  ridges  for  one  inch  of 
length.  If  the  number  is  6,  8,  10,  etc.,  this  gives  the  fraction 
of  an  inch  occupied  by  the  length  of  one  thread,  or  the  pitch. 
If  there  is  no  model  and  the  bolt  is  standard,  consult  a  Table 
of  Standard  Bolts  and  Nuts,  which  will  give  the  number  of 
threads  per  inch  for  the  diameter  of  bolt  required. 

A  Table  of  Standard  Bolts  and  Nuts  for  the  United  States 
Navy  is  found  at  the  end  of  the  book. 

Lay  off  this  length  on  the  left  side  of  the  bolt  and  draw 
two  horizontal  lines  through  the  marks.  Since  the  thread 
must  advance  longitudinally  one-half  of  one  of  these  division: 
for  the  half  revolution,  one-half  this  height  will  show  the  limit- 
ing height  of  the  right-hand  end  of  the  line.  See  Fig.  52. 

The  lines  through  a  and  b  are  apart  a  distance  equal  to  the 
pitch.  The  line  through  c  is  at  the  half- pitch.  Then  ad  is 
the  line  sought. 

As  a  rule,  the  slope  of  the  line  may  be  determined  with 


66 


ME  CHA  NIC  A  L   DRA  WING. 


sufficient  accuracy  by  eye.  As  the  height  of  this  line  longi- 
tudinally is  one  half-pitch,  double  this  height  must  separate 
the  lines  longitudinally.  See  Fig.  53. 

After  drawing  ad  with  the  slope  determined  by  eye,  project. 
d  across  to  b\  double  ab\  ac  is  the  pitch,  and  the  next  line 
begins  at  c. 


FIG.  52. 


FIG.  53. 


After  having  determined  the  position  of  the  lines  for  the 
top  of  the  thread  the  lines  for  the  bottom  may  be  drawn  as 
above. 

When  a  bolt  is  turned  to  the  right,  or  so  that  the  top  of  a 
thread  moves  to  the  right  and  down,  or  in  the  direction  of  the 
hands  of  a  watch,  the  thread  on  the  bolt  is  called  a  "right- 
handed  thread."  All  of  those  drawn  are  right-handed.  The 
slope  is  the  opposite  for  the  "left-handed  thread."  These 
left-handed  threads  are  used  only  for  special  purposes. 

When  a  section  is  cut  through  the  center  of  a  threaded 
hole,  the  part  of  the  female  thread  seen  beyond  the  section 
corresponds  to  the  hidden  part  of  the  thread  on  a  bolt,  and  the 
slope  is  in  the  opposite  direction.  The  shading  of  the  female 
thread  is  the  same  as  that  of  the  male  thread,  the  heavy  line 
at  the  bottom  of  the  thread. 

When  the  section  goes  through  the  bolt  in  position  in  the 
bolt-hole,  the  bolt  is  drawn  in  elevation  resting  in  the  section. 
As  a  rule  the  threads  are  not  drawn  and  the  bolt  and  hole  are 
represented  as  in  Fig.  54.  As  the  drill  used  for  drilling  the 
hole  is  ground  at  an  angle  of  60°,  the  bottom  of  the  hole  is 


GENERAL   DIRECTIONS. 


67 


finished  by  the  two  lines  making  an  angle  of  120°  with  each 
other.  The  end  of  the  bolt  is  rounded  off  as  a  rule,  the 
common  radius  being  the  diameter  of  the  bolt.  The  bolt  is 


FIG.   54- 

represented  as  screwed  to  the  bottom  of  the  cylindrical  part  of 
the  hole. 

Square  Threads. — The  threads  drawn  in  the  figures  are  all 
triangular,  which  is  the  common  type ;  but  square  threads  are 
used  for  many  special  purposes.  The  only  difference  is  in  the 
shape  of  the  thread.  The  pitch  and  methods  of  finding  the 
curves  for  the  top  and  bottom  are  the  same, 

I    ' 


Pitch 


FIG.  55- 

The  pitch-length  outside  the  solid  metal  is  filled,   in  the 
case  of  the  triangular  threads,  with  a  triangular-shaped  figure 


68 


MECHANICAL   DRAWING. 


and  a  space  of  nearly  the  same  shape.  In  the  case  of  square 
threads  the  portion  for  the  metal  and  the  space  remaining  are 
both  rectangular.  These  may  be  equal  and  may  differ  greatly, 
as  in  Fig.  55. 

These  threads  are  represented  as  in  the  case  of  triangular 
threads.  When  the  drawing  is  large  and  ornamental,  the 
helices  are  drawn ;  ordinarily  straight  lines  are  used.  The 
lines  for  the  depressed  portions  may  be  left  out  as  a  rule.  See 
Fig.  56. 


FIG.  56. 

The  pitch  may  be  taken  up  by  a  single  thread,  when  the 
thread  is  called  ' '  single  screw  "  ;  or  the  length  of  the  pitch 
may  be  filled  by  two  or  more  threads,  when  the  thread  is  called 
"  double  screw,"  "  triple  screw,"  etc. 

To  determine  to  what  class  a  screw  belongs,  follow  a  ridge 


FIG.  57- 

around  for  one  revolution  and  find  how  many  ridges  there  are 
between  the  original  point  and  the  one  arrived  at  after  going 
around.  Double,  triple  screws,  etc.,  are  used  when  a  greater 


GENERAL  DIRECTIONS. 


69 


longitudinal  movement  is  desired;  in  other  words,  when  the 
pitch  is  increased.  Then  the  space  between  the  following 
threads  is  filled  in  by  extra  threads  for  strength. 

Fig.  57  shows  a  single  screw  of  great  pitch. 

It  is  noticed  that  most  of  the  bolt  is  cylindrical.  For 
strength,  there  are  placed  between  the  threads  two  extra  ones 


I*-    Pitch 


FIG.  58. 


that  have  the  same  pitch  as  the  original  one.  Fig.  58  shows 
a  triple  screw  as  usually  drawn. 

When  the  threads  are  double  or  triple,  or  when  the  thread 
is  other  than  standard,  it  is  stated  on  the  drawing  near  the 
bolt. 

Hidden  threads  are  never  drawn  except  in  the  case  of  very 
large  threads  inside  of  nuts,  as  in  the  case  of  a  propeller  nut. 
In  this  case  the  threads  are  shown  in  broken  lines,  unshaded. 

When  threads  are  drawn  on  bolts,  it  is  seldom  advisable 
to  make  the  exact  ending  of  the  threads  as  it  is  in  reality. 


FIG.  59. 

The  tops  and  bottoms  of  threads  are  ended  as  in  the  sketch. 
The  real  ending  of  the  top  of  the  thread  is  behind  the  bolt 
somewhere.  The  bottom  has  to  be  ended  according  to  how  the 
curve  or  other  line  at  the  bottom  cuts  the  teeth  of  the  thread. 


MECHANICAL    DRA  WING. 


Bolts  and  Nuts. — As  most  bolts  are  standard,  the  dimen- 
sions are  obtained  from  the  Table  of  Standard  Bolts  and  Nuts. 
If  the  bolt  differs  from  the  standard,  the  points  of  difference 
are  shown  on  the  drawing. 

The  diameter  of  the  bolt  is  determined  either  by  calcula- 
tions for  strength  or  by  custom.  The  ordinary  bolts  used  in 
machine  work  have  hexagonal  heads ;  the  square-headed  bolts 
are  used  for  rough  work  or  for  special  purposes.  The  height 
of  the  bolt-head  and  the  long  and  short  diameters  are  given  in 
the  Table.  The  length  of  the  bolt  is  determined  by  the  neces- 
sities of  the  special  case.  After  the  head  of  the  bolt  is  shaped, 
the  top  edge  is  chamfered  off  at  an  angle  of  45°.  This  is  done 
by  centering  the  bolt  in  a  lathe  and  cutting  the  chamfer  as  the 
bolt  revolves.  This  chamfer  as  a  rule  is  cut  just  enough  so 
that  the  sharp  corners  are  removed,  and  so  that  the  flat  sides 
are  left  at  the  full  height  at  the  center.  This  is  shown  in 
Fig.  60. 


9 

"f 

SNJ 

^ 

1 

a 

s 

5 

FIG.  60. 


The  point /shows  that  the  middle  of  the  flat  side  is  left  at 
its  full  height,  while  at  g  the  sharp  corner  is  cut  off.     The 


GENERAL   DIRECTIONS. 


chamfer  makes  a  cone  of  revolution  which  cuts  the  flat  sides ; 
the  curves  of  intersection  are  hyperbolae;  but  the  projections 
of  these  hyperbolae  are  so  nearly  circles  that  they  are  drawn  as 
circles.  Where  the  cone  of  chamfer  cuts  the  top  plane,  the 
intersection  is  a  circle,  as  shown  in  the  plan  view. 

The  exact  representation  of  the  top  of  the  bolt  or  nut  is 
shown  in  Fig.  61,  but  the  45°  lines  are  seldom  drawn  in 
practice. 

From  the  Table  of  Standard  Bolts  and  Nuts  it  is  found 
that  the  height  of  the  nut  is  the  same  as  the  diameter  of  the 
bolt,  while  the  height  of  the  bolt-head  is  less,  as  a  rule. 


FIG.  61.  FIG.  62. 

In  drawing  the  nut,  from  the  point  a  with  a  radius  equal 
to  the  diameter  of  the  bolt  describe  an  arc,  as  shown.  See 
Fig.  62.  This  is  approximately  the  curve  for  the  middle  por- 
tion; the  continuation  of  this  curve  defines  the  limits  of  the 
long  diameter  of  the  nut.  The  continuation  of  the  lines  of  the 
bolt  defines  the  limits  of  the  central  face.  Draw  the  four  verti- 
cals and  a  horizontal  line  cf  through  <?.  Draw  a  vertical  center 
line  for  the  face  be  by  means  of  small  arcs  from  c  and  *?,  and 
find  a  center  on  this  line  that  will  cause  an  arc  to  pass  through 
the  points  c  and  ^  and  tangent  to  the  top  line.  Note  that,  as 
usually  drawn,  the  line  across  the  top  of  the  nut  ends  at  and 
is  tangent  to  the  top  of  the  curves  for  the  side  faces,  and  is 
tangent  to  the  curve  of  the  middle  face. 

In  drawing  the  head  of  the  bolt  (see  Fig.  60),  the  height 
is  laid  off  from  the  Table  and  the  top  line  drawn.  From  the 


MECHANICAL   DRAWING. 


center  of  this  top  line  lay  off  along  the  center  line  of  the  bolt 
the  distance  d. 

Beginning  with  this  point,  a,  as  in  the  case  of  the  nut,  find 
the  centers  for  the  side  faces. 

Tc^draw  the  other  view  of  the  bolt-head  (Fig.  60),  the 
widths  of  the  faces  are  projected  from  the  plan,  and  the  points 
where  the  curves  begin  are  projected  from  the  other  view 
drawn.  These  curves  must  have  centers  in  the  middle  lines 
of  the  faces  and  must  be  tangent  to  the  top  line.  The  center 
is  generally  found  by  trial,  but  the  length  of  the  radius  is  about 
four-fifths  of  the  diameter  of  the  bolt. 

Although  Fig.  60  shows  the  correct  way  to  represent  a 
bolt  according  to  the  general  plan,  it  is  customary  to  place  the 
Side  Elevation  under  the  Plan.  The  reason  is  that  the  Front 
Elevation  cannot  be  drawn  until  the  Side  Elevation  is  com-  / 
pleted,  as  the  limits  of  the  curves  have  to  be  determined  from 
the  Side  Elevation.  Hence  it  is  the  custom  always  to  draw 
the  Side  Elevation  of  Fig.  60  first  for  any  representation  of  a 
bolt.  If  two  views  of  the  bolt  are  made,  the  second  one  drawn 
is  the  Front  Elevation  of  Fig.  60.  In  other  words,  the  first 
view  shows  the  long  diameter  of  the  bolt-head. 

In  the  Plan  it  is  not  good  practice  to  draw  a  broken  line  to 
show  the  diameter  of  the  bolt. 

Where  a  number  of  bolts  or  nuts  are  drawn,  either  in  a 
straight  line  or  in  an  arc  of  a  circle,  the  heads  always  face  the 
same  way,  whether  in  Plan  or  Elevation ;  the  faces  of  the  nuts 
are  drawn  facing  in  the  same  way  as  the  bolts  for  each  view. 


\ 


FIG.  63. 

Sometimes  bolts  are  made  with  square  shoulders  under  the 
head  so  that  they  will  not  turn  when  in  place.      The  conven- 


GENERAL   DIRECTIONS. 


73 


tional  way  of  representing  this  square  portion  at  any  part  of  a 
body  generally  cylindrical  is  shown  in  Fig.  63. 

The  portion  with  the  crossed  lines  is  the  flat-sided  portion. 

For  rough  work  only,  where  the  nuts  are  stamped  out  and 


FIG.  64. 

unfinished,  the  nuts  are  screwed  on  the  bolts  with  the  rounded 
side  down,  as  in  Fig.  64. 

Bolts  that  are  finished  always  have  the  bottom  portion 
slightly  cut  away  at  the  projecting  corners,  so  that  these 
corners  will  not  cut  into  the  metal. 

When  bolts  and  nuts  are  drawn  in  place,  the  bolt  is  repre- 
sented as  projecting  beyond  the  nut  slightly.  When  threads 
are  drawn  on  the  bolt  beyond  the  nut,  represent  the  extension 


FIG.  66. 


FIG.  65. 

of  the  bolt  as  in  Fig.  65.      The  bottom  of  the  thread  is  pro- 
jected to  the  top  of  the  nut  on  either  side  of  the  center.     An 


74  MECHANICAL   DRAWING. 

arc  is  drawn  through  these  two  points,  using  the  middle  point 
of  the  bottom  of  the  nut  as  a  center. 

When  threads  are  merely  represented  on  the  bolt,  show 
the  extension  of  the  bolt  as  in  Fig.  66. 

The  outside  diameter  of  the  bolt  is  projected  to  the  top  of 
the  nut,  and  short  lines  are  drawn  and  an  arc  drawn  across  with 
a  radius  equal  to  the  outside  diameter  of  the  bolt.  The  height 
of  the  short  lines  drawn  varies  with  the  diameter  of  the  bolt. 

Jam-nuts. — These  are  two  nuts  screwed  tight  together  on 
a  bolt,  each  one  preventing  the  other  from  turning.  These 
are  generally  of  different  thicknesses  and  are  represented  as  in 
Fig.  67. 


FIG.  67. 

The  nut  nearest  the  end  of  the  bolt  is  thicker  than  the  first 
one  screwed  on.  Both  edges  of  both  nuts  are  chamfered. 

When  bolts  are  standard,  the  dimensions  given  are 
diameter,  length  under  head,  and  length  of  the  threaded 
portion. 

When  bolts  are  not  standard,  in  addition  to  the  above 
there  are  given  the  height  of  the  head,  either  the  long  or 
short  diameter  of  the  head,  and  the  number  of  threads  to  the 
inch. 

Tails. — When  two  curved  surfaces  meet  at  angles  with 
rounded  corners  to  prevent  sharp  angles  and  so  that  the  defin- 
ing lines  of  one  of  them  disappear,  it  is  customary  to  represent 
this  effect  by  short  curved  endings  called  4 '  tails. ' '  The  small 
projections  represent  bosses  for  bolts  and  are  cylindrical. 
They  gradually  meet  the  rounded  larger  surface  with  small 


GENERAL   DIRECTIONS. 


75 


curves  at  the  junction.      "  Tails"   are  placed  at  the  ends  of 
the  vertical  lines  to  represent  this  effect. 


1  -3 

>    -< 

> 

FIG.  68. 

Working,  Border,  and  Cutting  Lines — The  working  line 
encloses  a  rectangle  beyond  which  the  drawing  may  not 
extend,  as  a  rule.  It  is  laid  off  from  the  center  of  the  paper 
both  ways,  using  the  32  scale.  The  center  is  found  by  draw- 
ing with  the  T  square  diagonals  from  opposite  corners  of  the 
paper  (not  the  board).  This  line  is  pencilled  but  not  inked. 
The  idea  of  it  is  to  leave  a  space  between  the  drawing  and  the 
border  line  for  a  good  effect  and  to  avoid  confusion.  In 
special  cases,  where  the  scale  of  the  drawing  would  have  to  be 
made  too  small  on  account  of  this  line,  it  may  be  surpassed. 

The  border  line  is  ornamental  only  in  that  it  gives  a  finish 
to  the  general  effect  of  the  drawing,  and  the  blank,  irregular 
spaces  of  the  paper  beyond  the  drawing  are  made  less  promi- 
nent. 

This  line  is  drawn  in  pencil  after  the  working  line  is  drawn, 
and  is  at  a  certain  distance  outside  of  the  working  line.  It  is 
inked  after  the  drawing  is  completed.  Border  lines  are  often 
very  ornamental,  and  much  time  and  care  may  be  expended 
on  them  when  an  especially  ornamental  drawing  is  to  be  made ; 
but,  as  a  rule,  little  time  may  be  put  upon  them,  as  other  work 
is  more  important. 

It  is  a  good  effect  to  shade  the  lower  and  right-hand  border 
lines.  The  upper  and  left-hand  lines  are  made  of  fair  width, 
and  the  other  lines  at  least  four  times  as  heavy.  Plain  lines 
meeting  at  points  are  sufficiently  effective.  Occasionally  small 


70  MECHANICAL   DRAWING. 

portions  of  the  drawing  may  project  beyond  the  border  line. 
In  this  case  interrupt  the  border  line  for  half  an  inch  on  either 
side  of  the  outline  passing  beyond  it. 

The  cutting  line  is  outside  of  the  border  and  is  drawn  in 
pencil  after  the  border  line  is  marked.  This  line  is  simply  a 
guide  for  cutting,  and  is  not  inked.  When  the  line  is  drawn, 
it  may  be  found  that  portions  of  the  paste  used  in  stretching 
the  paper  may  be  so  far  in  that  there  will  be  difficulty  in 
cutting  off  the  paper  finally;  in  this  case,  all  the  lines  may  be 
moved  farther  away  from  this  side ;  or  it  may  be  necessary  to 
change  the  dimensions  of  working,  border,  and  cutting  lines, 
as  is  most  convenient. 

In  marking  the  working,  border,  and  cutting  lines,  the  half- 
distances  enclosed  by  these  lines  are  laid  off  vertically  and 
horizontally  along  center  lines  drawn  in  these  directions 
through  the  center  of  the  paper.  These  distances  are  marked 
once  only.  The  T  square  and  triangles  are  depended  upon 
for  accurate  lines. 


a  a,  Cutting  Lines 
b  6,  Border       »«• 
cc,  Working   « 


FIG.  69. 

Legend,  Lettering,  Scale,  etc. — The  legend  refers  to  the 
description  of  the  drawing,  with  the  scale  and  the  name  of  the 


GENERAL   DIRECTIONS.  77 

one  who  made  the  drawing.  All  these  records  are  placed  in 
the  lower  right-hand  (S.  E.)  corner  of  the  drawing  inside  the 
working  edge,  and  space  must  be  left  for  them  when  calculat- 
ing on  the  best  arrangement  of  the  different  views.  This 
generally  leaves  a  blank  space  along  the  upper  right-hand  edge 
of  the  paper,  but  the  effect  of  the  drawing  as  a  work  of  art  is 
sacrificed  to  utility.  As  drawings  are  stored  in  drawers  and  it 
must  be  possible  rapidly  to  find  the  one  sought,  the  descrip- 
tions must  be  in  the  same  place  in  all,  and  they  must  be  at 
one  of  the  lower  corners,  so  that  it  may  be  possible  to  read 
them  without  pulling  out  each  sheet.  By  raising  the  right- 
hand  corners  of  a  number  of  drawings,  the  legends  may  be 
rapidly  looked  at  and  the  one  desired  found  with  the  least  loss 
of  time. 

In  the  S.  E.  corner  is  placed  the  general  description  of  the 
drawing  or  drawings  on  the  board.  If  a  number  of  objects  are 
shown,  find  as  generic  a  name  as  possible  for  them  all,  but  one 
that  will  leave  no  uncertainty  as  to  what  may  be  on  the  draw- 
ing. Besides  the  very  general  description  in  the  S.  E.  corner, 
place  near  (under,  if  convenient)  each  different  drawing  any 
especial  remarks  that  may  be  necessary  to  more  thoroughly 
describe  it. 

When  drawings  are  made  from  brass  models,  after  the 
name  of  the  object  the  legend  reads :  ' '  Sketched  and  drawn 
from  models." 

When  drawings  are  made  from  portions  of  machinery,  after 
the  name  of  the  object  the  legend  reads :  ' '  Sketched  and 
drawn  from  work. ' ' 

When  drawings  are  made  from  blue-prints  of  general 
arrangements,  first  give  the  name  of  the  ship  (Battleship  Iowa, 
Cruiser  Detroit,  U.  S.  S.  Adams,  etc.),  then  the  description 
of  the  object  or  objects ;  after  that  the  legend  reads :  '  *  Taken 
from  blue-print  of  General  Arrangement  of  Machinery. ' ' 

If  all  the  drawings  on  the  sheet  are  taken  from  the  same 
work,  the  legend  in  the  S.  E.  corner  may  contain  the  re- 


78  MECHANICAL    DRAWING. 


« 

I 

c  § 


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CD      9)     §>   " 
CD 


I    I 


GENERAL   DIRECTIONS.  79 

marks  showing  whence  the  material  for  the  drawing  came ;  in 
case  the  drawings  are  from  different  sources,  the  special  re- 
marks are  placed  near  the  different  drawings. 

In  the  legend,  the  sequence  of  the  different  portions  is  as 
follows : 

Name  of  object  represented. 
Special  remarks. 

Scale. 

Name.          Class. 
Date. 

The  name  of  the  object  is  made  in  some  type  of  heavy 
lettering  and  is  the  prominent  part  of  the  legend.  When  a 
ship's  name  or  number  is  given,  this  is  equally  prominent.  All 
the  rest  of  the  lettering  is  done  with  a  writing-pen,  the  letters 
small  and  clear.  The  name  is  not  prominent  and  is  an 
autograph. 

Block  Letters. — This  is  the  type  of  lettering  preferred  for 
heavy  type.  The  letters,  as  a  rule,  are  three  spaces  wide  and 
all  are  five  spaces  high,  as  shown  in  the  sketch,  while  one 
space  separates  the  letters.  The  letters  M  and  W  occupy  re- 
spectively four  and  five  spaces,  as  shown.  The  peculiarity  of 
the  letter  K  is  shown.  The  peculiarities  of  the  figures  are  also 
shown. 

Numerous  variations  of  these  letters  may  be  made  by  vary- 
ing the  heights,  widths,  slopes,  etc.,  of  the  spaces;  by  making 
solid  or  skeleton  letters ;  by  drawing  shade  lines ;  by  drawing 
the  shade  lines  only;  by  shading  in  any  direction  and  to  any 
extent,  etc. 

Sample  drawings  of  these  letters  are  found  in  the  drawing- 
room. 

When  block  lettering  is  to  be  used,  measure  the  length  of 
space  that  is  available  and  draw  a  vertical  center  line.  Make 
a  rough  copy  of  the  letters  to  go  on  one  line  on  a  spare  piece 
of  paper.  Allow  the  spaces  between  the  words  and  place 


8o 


MECHANICAL   DRAWING. 


GENERAL   DIRECTIONS. 


81 


82  MECHANICAL   DRAWING. 

figures  over  each  letter  and  the  following  space  for  the  number 
of  the  spaces  actually  needed.  Half  the  sum  of  these  figures 
gives  the  part  of  the  lettering  to  coincide  with  the  center  line 
drawn.  From  the  half- width  of  the  space  available  and  the 
half-number  of  spaces  required,  the  width  of  one  space  is  cal- 
culated. The  next  smaller  division  on  a  regular  scale  may  be 
used  and  the  spaces  laid  off  from  the  triangular  scale ;  or  the 
exact  width  desired  may  be  obtained  very  closely  and  this  dis- 
tance laid  off  with  the  bow  spacers  on  a  line  just  below  the 
one  for  the  bottom  of  the  letters.  The  vertical  lines  for  the 
spaces  may  then  be  drawn  and  the  height  chosen  for  the  ver- 
tical spaces.  For  ordinary  work  letters  need  not  be  over  half 
an  inch  high,  and  three-eighths  of  an  inch  is  amply  large  for 
most  drawings. 


1 

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/ 

1 

y 

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Another  type  of  block  letters  is  shown.  In  this  case, 
decide  on  the  total  width  allowable  for  each  letter  and  its  fol- 
lowing space,  and  lay  off  these  total  spaces;  then  decide  on 
how  much  of  these  total  spaces  shall  be  letter  and  how  much 
distances  between  letters.  Divide  the  laid-off  spaces  accord- 
ingly. Draw  horizontal  lines  for  determining  the  beginnings 
of  the  slopes  at  any  desired  distances  from  the  top,  middle. 


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GENERAL   DIRECTIONS.  83 

and  bottom  lines.  Where  these  lines  cut  the  vertical  bounding 
lines  of  the  letters  the  angular  lines  begin.  The  slopes  may 
be  varied,  the  slopes  made  arcs,  and  the  slant  of  the  lines 
may  be  changed  as  desired,  but  for  ordinary  drawings  the 
simple  type  is  best.  These  letters  are  generally  drawn  with 
an  opening  of  the  pen  that  will  ensure  a  good  line  that  may 
be  continued  indefinitely  and  that  is  at  the  same  time  quite 
heavy. 

Free-hand  Lettering. — There  are  many  types  of  free-hand 
lettering,  but  the  simplest  and  most  clear  and  the  easiest  made 
are  the  best.  No  time  should  be  wasted  on  the  lettering,  but 
it  must  be  distinct.  The  samples  given  are  very  satisfactory 
and  are  much  used.  A  little  practice  brings  a  fair  proficiency. 
It  is  well  to  draw  the  top  and  bottom  guide-lines  for  the  capi- 
tals as  well  as  the  small  letters. 

The  height  of  the  small  letters  is  about  £",  and  of  the 
capitals  -&". 

The  figures  are  the  same  height  as  the  capitals. 

Variation  may  be  made  in  the  slope  of  the  letters  and  indi- 
vidual designs  used  to  a  certain  extent,  but  the  simpler  and 
more  upright  the  letter  the  better. 

Use  an  ordinary  writing-pen.  Try  many  kinds  until  the 
most  satisfactory  result  is  obtained.  Always  make  the  letters 
and  figures  distinct. 

After  the  drawings  of  brass  models  are  completed,  the 
different  views  are  no  longer  marked  "  Plan,"  "  Front  Eleva- 
tion," etc.,  as  it  is  supposed  that  all  are  familiar  with  the  dif- 
ferent views  by  that  time. 

Scales. — The  scale  of  the  drawing  is  clearly  stated.  If 
only  one  scale  is  used  throughout  the  drawing,  this  scale  is 
given  in  the  legend.  If  different  scales  are  used  in  different 
parts  of  the  drawing,  the  various  scales  are  placed  near  the 
drawings  where  used,  generally  under  them,  so  that  there  may 
be  no  possibility  of  error. 


84  MECHANICAL    DRAWING. 

Scales  are  stated  as  follows:    Scale,  3"  =  i  foot;   £ 
foot;  etc. 

Scales  other  than  those  on  the  triangular  scale  are  stated : 
Scale,  full  size;  scale,  half  size;  scale,  three-quarter  size; 
scale,  double  size. 

Never  state:  Scale,  f  size.  Always  write  out  the  frac- 
tion. 

Never  state:  Scale,  9"  =  i  foot;  or,  Scale,  8"  =  i  foot; 
as  there  are  no  such  scales  on  the  triangular  scales  used. 

Line  Shading  and  Tinting.— Line  shading  and  tinting  are 
used  for  ornamental  drawings,  and  to  show  more  clearly  to 
those  not  familiar  with  mechanical  drawing  the  intention  of 
the  views  and  the  arrangement  of  the  different  parts  of  the 
mechanism. 

As  shown  by  the  title,  the  surfaces  are  covered  with  lines 
or  tints  of  different  light  effects  to  show  as  clearly  as  possible 
how  the  object  really  appears. 

Line  Shading. — There  are  certain  prevailing  methods  of 
shading  surfaces,  and  these  methods  apply  to  all  views  of  an 
object. 

The  light  is  supposed  to  come  from  the  same  point  as 
under  "  Shade  Lines,"  that  is,  from  the  N.  W.  direction  and 
from  an  angle  of  45°  above  the  drawing-board. 

Flat  Surfaces. — Fig.  70  shows  two  positions  of  half  of  a 
hexagonal  prism  with  a  smaller  hexagonal  prism  cut  out 
centrally.  These  views  give  some  of  the  various  types  of  flat 
surfaces  to  be  considered. 

Flat  surfaces  parallel  to  the  paper  and  on  which  the  light 
falls  have  a  uniform  light  effect,  as  surfaces  A. 

Flat  surfaces  parallel  to  the  paper  and  on  which  the  light 
does  not  fall  have  a  uniform  dark  effect. 

Flat  surfaces  on  which  the  light  falls  and  which  are  inclined 
to  the  paper  have  a  light  effect  which  gradually  becomes  darker 
as  the  surface  recedes,  as  surfaces  B. 


GENERAL  DIRECTIONS. 


Flat  surfaces  on  which  the  light  does  not  fall  and  which 
are  inclined  to  the  paper  have  a  dark  effect  that  gradually 
becomes  lighter  as  the  surface  recedes,  as  surfaces  C. 

Generally  speaking,  striking  contrasts  are  made  at  the  front 
of  the  drawing:  the  parts  near  the  eye  are  in  high  light  and 


FIG.  70. 

•deep  shades,  while  those  parts  in  the  background  have  less 
contrast  as  they  are  farther  away,  the  parts  in  the  light  being 
less  bright,  and  those  in  the  shade  less  dark. 

To  Shade  a  Cylinder. — In  order  to  produce  the  rounded 
effect  of  the  cylinder,  lines  or  tints  are  graded  from  light 
effect  to  darker  ones.  The  heaviest  part  of  the  shade  is  theo- 
retically at  the  position  of  45°,  as  shown  in  Fig.  71.  The 
point  of  lightest  effect  is  theoretically  at  a  position  of  22^°,  as 
shown. 

It  is  not  deemed  necessary  to  study  the  reason  for  these 
points  of  light  and  shade.  After  these  points  are  determined, 
it  is  in  accordance  with  the  best  practice  to  move  these  posi- 
tions somewhat  in  order  to  produce  a  better  effect.  The 
darkest  part  is  moved  nearer  to  the  central  line  of  the  figure, 
and  the  lightest  part  is  moved  farther  away  from  this  center. 


86  MECHANICAL    DRAWING. 

The  amount  of  this  movement  is  proportional  entirely,  and 
Fig.  7 1  gives  about  the  right  amount.  After  finally  establishing 
the  dark  and  light  lines,  one  method  of  line  shading  is  shown 
in  the  above  figure.  In  this  case  all  the  lines  are  of  the  same 
breadth,  and  the  effect  of  rounding  is  produced  entirely  by 
varying  the  distances  apart  of  the  lines.  A  clear  line,  com- 


FIG.   71. 

paratively  fine,  is  chosen  and  the  lines  are  drawn  in  succession 
from  one  side  to  the  other,  the  gradations  of  space  being  made 
according  to  judgment.  It  seems  best  to  begin  at  the  side  of 
the  cylinder  nearest  to  the  lightest  line,  and  to  follow  along 
to  the  other.  The  effect  at  the  edges  should  be  exactly  the 
same. 

Fig.  72  shows  the  more  ornamental  and  effective  kind  of 
line  shading.  This  is  more  extensively  used  also.  The  dark 
and  light  portions  are  established  as  before,  and  the  rounding 
effect  is  produced  by  a  combination  of  varying  the  width  of 
the  lines  and  also  the  distances  apart.  Often  three  or  four 
of  the  darkest  lines  at  the  darkest  point  of  the  shading  are 
combined  in  one.  It  seems  best  to  begin  this  shading  on  the 
left  side — that  nearest  to  the  lighter  portion.  The  line  first 
drawn  should  be  well  chosen  and  in  accordance  with  the  size 
of  the  cylinder.  This  line  will  establish  the  weights  of  the 
other  lines  and  practically  whether  the  cylinder  will  be  shaded 
dark  or  light.  After  the  first  line,  the  others  are  varied 


GENERAL   DIRECTIONS. 


according  to  judgment.  At  times  three  or  four  lines  of  the 
same  width  are  drawn,  the  spaces  between  them  slightly 
varied.  The  combination  of  varying  the  width  of  the  lines  and 
the  width  of  the  spaces  gives  a  good  chance  to  round  the 


FIG.  72. 

cylinder  up  nicely.  At  the  end,  note  that  there  is  always  a 
light  effect  near  the  edge  last  finished.  There  is  a  slightly 
wider  space  left  between  the  last  two  lines  and  the  others  just 
drawn.  This  produces  the  effect  of  a  light  streak  just  near  the 
edge.  This  is  supposed  to  be  the  effect  of  reflected  or  diffused 
light  coming  around  the  side  of  the  cylinder. 

This  effect  is  never  shown  at  the  other  side  of  the  cylinder; 
the  shading  there  is  gradual  to  the  very  edge. 


88 


MECHANICAL    DRAWING. 


Interior  of  a  Hollow  Cylinder. — As  shown  in  Fig.  73,  the 
heavy  part  of  the  shading  commences  at  the  edge  in  shadow 


FIG.  73. 

and  grades  to  the    lightest    part,   found  as  before;    then    the 
shading  continues  to  the  other  side  gradually. 


A  Cone. — The  dark  and  light  points  are  established  as  in 
the  case  of  the  cylinder  and  the  same  system  is  followed.  In 
the  heavy  type  of  shading  each  of  the  shade  lines  becomes  a 
triangle.  The  light  effect  at  the  side  nearest  to  the  heavy 


GENERAL    DIRECTIONS. 


89 


FIG.  74- 

shade  lines  is  preserved  as  in  the  case  of  the  cylinder.     It  is 
found  advisable  in  shading  the  cone  to  draw  the  lines  from  the 


FIG.  75- 


90  MECHANICAL    DRAWING. 

apex  and  to  begin  at  the  heaviest  shading,  working  both  ways. 
Many  lines  are  not  begun  at  the  apex  but  a  little  below,  to 
avoid  a  blot.  When  all  the  lines  are  drawn,  the  light  spaces 
near  the  apex  are  filled  in  with  a  fine  opening  of  pen. 

A  Sphere. — The  darkest  and  lightest  points  are  on  the 
45°  line  as  shown,  and  their  approximate  radial  positions 
determined  by  eye.  See  Fig.  75. 

These  lines  are  drawn  as  show  n  under  ' '  Shade  Lines. ' ' 
A  horn  center  should  be  used. 


FIG.  76. 


GENERAL  DIRECTIONS.  QI 

Another  method.  (Fig.  76.)  This  does  not  produce  the 
true  effect,  as  the  varying  lights  traverse  the  surface  in  zones, 
but  it  is  much  easier  to  make  and  is  much  used.  The  center 
of  the  arcs  is  the  center  of  the  lightest  portion. 

Tinting. — The  same  methods  of  arranging  the  lights  and 
shadows  of  the  shading  apply  to  the  tinting. 

Tinting  may  be  done  with  any  colors  or  with  Indian  ink. 
Colors  are  seldom  used;  and  as  the  same  methods  apply,  the 
description  of  the  method  of  using  Indian  ink  will  answer. 
Use  stick  Indian  ink — not  the  ink  mixed  in  bottles. 

The  paper  must  be  stretched  on  the  board  if  tinting  is  to 
be  done.  The  drawing  must  be  kept  as  clean  as  possible,  and 
the  rubber  not  used,  as  it  roughens  the  surface  of  the  paper. 
The  tinting  is  done  after  the  black  lines  of  the  drawing  are 
completed  without  shade  lines.  The  drawing  is  then  washed 
in  running  water — not  rubbed — and  is  allowed  to  dry. 

To  Prepare  the  Tint. — At  least  two  brushes  are  needed; 
two  beakers  or  water-glasses  partly  filled  with  clean  water ;  an 
ink-slab  or  saucer  in  which  to  mix  the  ink ;  a  stick  of  Indian 
ink;  and  a  piece  of  blotting-paper. 

Clean  all  these  articles  thoroughly.  Decide  on  the  amount 
of  liquid  ink  necessary  according  to  the  quantity  of  surface  to 
be  covered.  Place  sufficient  water  in  the  ink-saucer  and  pro- 
ceed to  grind  the  ink  in  the  water  by  rubbing  it  about  with  a 
certain  pressure  on  the  bottom  of  the  saucer.  This  requires 
considerable  time,  as  the  ink  dissolves  slowly.  It  should  be 
ground  until  a  line  made  with  it  by  the  R.  L.  pen  remains 
black  when  dry.  This  ink  is  now  in  condition  to  be  used  for 
drawing.  As  the  ink  used  in  tinting  is  very  much  lighter  in 
color,  the  ink  mixed  will  serve  to  cover  from  three  to  four  times 
the  surface  that  it  would  cover  if  used  in  its  black  state.  In 
one  of  the  water-glasses  or  beakers  place  a  small  quantity  of 
water ;  dip  the  brush  in  the  top  of  the  mixed  ink,  so  as  to  take 
up  only  the  clear  ink  and  leave  the  sediment,  and  stir  this  color 


92  MECHANICAL    DRAWING. 

into  the  water  in  the  beaker.  With  a  brush  test  the  color  of 
the  tint  on  a  piece  of  drawing-paper,  allowing  the  color  to  dry. 
Add  black  ink  until  the  tint  is  as  desired.  The  tint  chosen 
should  be  much  lighter  than  will  be  the  final  effect  on  the 
drawing,  as  it  is  very  easy  to  darken  the  drawing  by  laying  on 
another  tint,  while  it  is  very  difficult  to  repair  work  that  is  too 
dark. 

Take  a  clean  brush  and  clean  water  and  carefully  go  over 
the  surface  to  be  tinted  with  this  water;  be  particularly  careful 
that  the  edges  are  moist  to  the  boundary  lines  and  that  these 
are  not  passed,  as  the  tint  will  follow  all  these  defects. 

To  Lay  on  a  Flat  Tint. — This  seems  easy  but  is  extremely 
difficult,  and  methods  differ  also.  Some  leave  the  drawing- 
board  level  and  others  tip  it  slightly,  so  that  the  bottom  of  the 
board  is  three  inches  or  more  lower  than  the  top.  Draftsmen 
follow  the  methods  that  suit  them  best.  The  same  general 
plan  is  followed  in  either  case,  only  that  it  is  thought  that  when 
the  board  is  tipped  the  tint  flows  by  gravity  and  assists  the 
operation.  However,  as  it  is  difficult  to  tip  the  board  in  all 
the  directions  required  in  making  a  complicated  drawing,  it  is 
well  to  learn  to  tint  with  the  board  horizontal. 

After  a  space  has  been  moistened  slightly  with  the  clean 
water,  dip  a  brush  deeply  into  the  prepared  tint  and  stir  it  well 
around  so  that  it  is  permeated  with  the  same  shade  of  color; 
either  keep  the  brush  full  for  a  large  surface,  or  for  a  small  one 
remove  part  of  the  liquid  by  rubbing  the  brush  on  the  edge  of 
the  glass;  according  to  the  shape  of  the  surface,  carry  the 
brush  along  one  line  rapidly  and  carefully;  before  this  has  a 
cnance  to  dry,  run  the  brush  again  along  in  the  same  direction 
but  a  little  farther  on  from  the  edge,  thus  making  the  surface 
moistened  twice  as  wide  as  before;  continue  in  this  way,  never 
allowing  an  edge  to  dry  until  the  whole  surface  has  been 
covered;  at  the  end,  if  there  is  too  much  of  the  tint  on  the 
paper,  quickly  dry  the  brush  by  rubbing  it  on  a  piece  of 
blotting-paper  and  then  use  it  to  dry  up  the  last  part  of  the 


GENERAL  DIRECTIONS..  93 

work.  If  carefully  done,  it  will  be  found  that  a  perfectly  even 
coat  of  color  has  been  placed  on  the  surface.  If  this  tint  is  not 
dark  enough,  it  maybe  darkened  by  successive  tintings ;  but 
never  put  on  a  second  tint  until  the  first  one  is  "hand  dry," 
or  dry  to  the  touch.  Never  try  to  touch  up  a  small  portion  of 
the  surface  except  by  "  stippling,  "  which  alters  the  entire  effect 
of  the  work. 

When  using  the  brush  along  the  boundary  lines  of  the 
space,  always  keep  the  point  of  the  brush  towards  the  edge. 
Do  not  bear  on  the  brush,  as  this  may  cause  marks  to  be  made 
that  will  show  under  the  tint. 

For  large  surfaces  lay  on  a  light  tint.  Reverse  the  board 
and  lay  on  a  second  one.  Turn  the  board  and  repeat  from 
one  side;  then  do  the  same  from  the  other  side.  This  does 
away  with  the  effects  of  streaks  in  any  one  direction,  and  the 
result  is  an  even  tint  over  the  whole  surface. 

Graduated  Tints. — There  are  two  general  methods,  the 
French  and  the  American. 

The  French  method  consists  in  dividing  up  the  space  to 
be  covered  into  small  rectangles  (these  must  not  be  marked 
with  pencil,  as  the  marks  cannot  be  eradicated);  putting  on  a 
tint  in  the  rectangle  to  be  darkest  and  allowing  it  to  dry; 
putting  on  a  tint  covering  the  rectangle  already  tinted  and  an 
adjacent  one  and  allowing  it  to  dry  again ;  and  continuing  this 
operation  until  the  entire  surface  is  covered.  By  this  method 
the  shading  is  in  streaks  that  are  more  or  less  prominent 
according  to  the  width  or  narrowness  of  the  rectangles.  This 
method  takes  too  much  time  also. 

The  American  method  is  most  used  and  takes  less  time, 
while  the  effect  is  equally  good.  This  is  called  the  method  of 
shading  by  softened  tints.  For  a  surface  that  is  flat  and 
inclined  at  an  angle. to  the  paper,  the  method  is  as  follows: 

Saturate  the  brush  as  before  with  the  tint  and  remove  most 
of  it  against  the  side  of  the  beaker;  lay  a  narrow  line  of  the 
tint  along  the  line  of  darkest  shade ;  while  this  is  still  wet  dip 


94 


MECHANICAL  DRAWING. 


FIG.  77. 


FIG.  78. 


FIG.  79. 


FIG.  80. 


GENERAL    DIRECTIONS. 


95 


FIG.  81. 


FIG.  82 


96  MECHANICAL  DRAWING. 

the  point  of  the  brush  in  c.lean  water,  which  dilutes  the  color 
on  the;  brush,  and  apply  a  line  along  the  edge  of  the  tint 
previously  laid  on,  rubbing  into  the  edge  of  the  other  tint; 
again  weaken  the  tint  and  continue  as  before.  Each  operation 
leaves  a  lighter  tint,  and  at  the  end  a  clean  brush  in  clear  water 
leaves  practically  no  color.  This  method  softens  the  grada- 
tions from  one  tint  to  another  and  is  rapidly  finished. 

When  the  surface  is  dry  the  operation  may  be  repeated  and 
thus  continued  until  the  desired  effect  is  produced. 

For  large  surfaces  it  is  well  to  mix  three  or  more  tints  of 
varying  darkness.  After  laying  on  the  first  line  of  the  darkest 
tint,  dip  the  brush  in  the  next  darkest  and  so  carry  on  the 
shading  until  approaching  the  light  edge,  when  finish  with  a 
clean  brush  and  clear  water. 

In  shading  cylinders,  cones,  and  spheres,  the  work  is  done 
very  rapidly,  as  the  dark  tint  is  first  laid  in  the  interior  of  the 
surface  and  the  shading  must  be  carried  away  from  the  edges 
of  this  first  tint  in  all  -directions  before  any  of  it  may  become 
dry. 

Stippling. — When  the  work  is  uneven,  as  is  often  the  case, 
due  to  irregularities  in  the  paper  and  lack  of  experience, 
stippling  may  be  resorted  to  to  improve  the  effect.  Fill  the 
brush  with  a  light  tint  and  remove  most  of  the  color;  touch 
the  lighter  portions  of  the  tinting  with  the  point  of  the  brush 
until  the  surface  is  brought  to  the  right  effect  by  these  points 
of  color.  After  stippling,  it  is  well  to  go  over  the  whole  sur- 
face with  an  even  light  tint  to  smooth  down  the  effect.  Many 
draftsmen  stipple  a  drawing  after  the  shading  is  complete,  as 
it  is  thought  to  improve  the  effect. 

Tracing. — If  more  than  one  copy  of  a  drawing  is  required, 
it  is  traced,  and  blue-prints  are  made  from  the  tracing.  The 
business  method  is  to  make  the  original  drawing  in  pencil  only; 
this  is  traced  in  ink,  and  the  tracing  is  kept  as  the  original. 
The  pencilled  drawing  is  not  retained. 

Tracing-cloth  or  paper  is  transparent;   it  is  tacked  in  place 


GENERAL   DIRECTIONS.  97 

over  the  drawing  as  described  under  '«  Thumb-tacks,"  and  the 
method  of  tracing  follows  the  method  of  inking  the  original 
drawing  as  described  under  "  Plan  of  Procedure." 

Tracings  are  made  on  the  smooth  or  shiny  side  of  the 
paper.  As  there  is  sometimes  trouble  in  getting  the  ink  to 
run  freely  on  the  tracing-cloth,  special  powders  are  furnished; 
dust  on  a  little  powder  and  rub  it  around  with  a  cloth. 
Electro-silicon  is  found  to  be  an  excellent  powder  for  this  pur- 
pose. A  blackboard-eraser  saturated  with  chalk  is  sometimes 
rubbed  gently  across  the  paper  for  the  same  purpose  and 
answers  as  well. 

The  tracing  is  completed,  lettering,  border  lines,  legend, 
etc.  It  is  then  removed  from  the  board  and  trimmed,  and  blue- 
prints are  made. 

Be  careful  not  to  wet  the  tracing. 

Errors  should  be  erased  only  with  the  rubber  ink-eraser. 
After  that,  rub  the  surface  with  a  soapstone  pencil  and  polish 
with  agate  or  other  hard  substance. 

Blue-printing. — The  tracing  is  placed  in  the  printing- 
frame,  the  shiny  or  drawing  side  next  the  glass ;  the  sensitive 
paper  is  placed  next  the  tracing,  the  sensitive  side  towards  the 
tracing ;  the  backing  is  .put  in  place  and  the  frame  placed  so 
that  the  sun's  rays  strike  normally.  Ordinarily  in  from  five  to 
ten  minutes  the  print  is  completed.  The  print  is  removed  from 
the  frame  in  as  dark  a  place  as  is  convenient,  and  is  then  placed 
face  down  in  a  bath  containing  clear,  running  water  sufficiently 
deep  to  cover  the  paper  well. 

The  print  is  moved  about  occasionally  and  remains  in  the 
water  about  fifteen  minutes.  The  action  is  made  more  rapid 
by  placing  a  small  quantity  of  ordinary  salt  in  the  water. 

The  print  is  now  dried,  preferably  by  being  tacked  at  the 
upper  edge  so  as  to  hang  vertically.  In  this  way  it  does  not 
become  curled  and  troublesome. 

These  blue-prints  are  now  the  working  drawings  used,  as 


98  MECHANICAL    DRAWING. 

many  copies  may  be  furnished;  the  original,  the  tracing,  is 
carefully  preserved. 

Line  shading  may  be  very  well  done  on  tracing-cloth,  but 
the  tinting  draws  the  cloth  out  of  shape  as  the  tint  dries.  So, 
instead  of  tinting,  colored  chalk  is  rubbed  on  the  back  of  the 
tracing. 

The  same  light  and  dark  effects  may  be  produced  as  with 
tinting,  and  the  blue-print  carefully  reproduces  these  effects. 

To  write  on  a  blue-print  (white  characters),  or  to  scratch 
out  or  wipe  out  any  portion  that  has  been  printed,  use  a 
saturated  solution  of  sal-soda  (washing-soda). 

If  the  blue  print  is  underexposed,  it  may  be  developed  by 
acetic  or  hydrochloric  acid  bath. 

The  ordinary  blue-print  consists  of  white  lines  on  a  blue 
ground.  Many  prefer  blue  or  black  lines  on  a  white  ground. 
This  is  accomplished  by  printing  from  the  tracing  on  special 
paper  a  "  negative  "  which  consists  of  white  lines  on  a  black 
ground.  By  using  this  "negative  "  instead  of  the  tracing,  a 
print  of  either  blue  or  black  lines  on  a  white  ground  may  be 
produced. 

Sketches. — Sketches  are  considered  one  of  the  most  impor- 
tant parts  of  the  course.  They  are  made  in  the  sketch-books, 
free-hand,  not  to  scale.  The  attempt  is  made  to  sketch  as 
well  as  possible  an  accurate  representation  of  an  object  in  the 
different  views  needed,  and  to  preserve  quite  accurately  the 
relative  proportions  of  the  object.  Dimensions  are  carefully 
taken  with  calipers  and  rule  only  and  are  clearly  marked  on 
the  sketches. 

The  idea  to  bear  in  mind  when  making  sketches  is  that 
there  will  be  no  further  opportunity  to  see  the  object  after  once 
the  sketch  is  completed ;  it  is  supposed  that  the  one  making 
the  sketch  is  on  detached  duty  and  must  make  a  sketch  so 
accurate  that  he  will  be  able  to  make  a  working  drawing  of  the 
object  at  any  later  date. 

No  instruments  whatever  are  used  in  making  the  sketches. 


GENERAL  DIRECTIONS.  99 

The  pencil  used  is  softer  than  HHHHHH  and  is  sharpened  to 
a  point,  and  should  be  kept  fairly  sharp  if  good  work  is 
attempted. 

The  first  sketches  are  made  on  the  lined  paper  in  the  front 
part  of  the  sketch-book.  This  assists  in  learning  how  to  make 
straight  lines  free-hand,  and  also  assists  in  drawing  lines  per- 
pendicular to  each  other  and  in  preserving  the  general  propor- 
tions of  the  sketches.  After  the  drawing  of  the  brass  models 
is  completed,  sketches  are  made  on  the  unlined  paper  in  the 
other  parts  of  the  book,  as  it  is  considered  that  all  may  have 
acquired  sufficient  ability  by  that  time,  and  the  lined  paper 
may  not  always  be  at  hand. 

The  sizes  of  the  sketches  are  not  in  proportion  to  the  size 
of  the  object  sketched,  but  are  large  enough  so  that  all  details 
may  be  shown  without  confusion  and  so  that  all  dimensions 
may  be  readily  placed  and  clearly  read. 

As  a  rule,  the  same  views  are  made  in  sketching  as  are  made 
on  the  drawing-board,  and  the  same  dimensions  that  are  placed 
on  the  sketch  are  eventually  placed  on  the  drawing.  In  the 
sketch,  however,  there  are  many  abbreviations  and  lessenings 
of  work.  It  is  sufficient  to  represent  a  portion  of  the  work. 
If  a  large  surface  is  to  be  hatched,  in  the  sketch  only  a  small 
portion  need  be  hatched,  as  it  is  understood  that  the  remainder 
must  be  treated  in  the  same  manner.  If  there  are  a  number 
of  threads  or  bolt-holes  of  the  same  kind,  it  is  sufficient  to 
sketch  one  of  them  carefully  and  indicate  the  number  and 
positions  of  the  others. 

The  first  thing  to  do  when  beginning  a  sketch  is  to  ex- 
amine the  object  and  decide  what  sketches  are  required  and 
then  decide  in  what  order  to  make  them.  If  the  book  is  suffi- 
ciently large,  the  general  plan  is  followed  and  the  points  are 
projected  from  one  drawing  to  the  other.  The  projecting  lines 
are  not  drawn.  There  may  be  a  choice  as  to  which  one  is 
drawn  first.  It  may  be  the  Plan,  the  Side  Elevation,  or  the 
Front  Elevation,  but  it  is  best  to  draw  first  the  one  that  gives 


100  MECHANICAL    DRAWING. 

the  best  general  idea  of  the  object  and  the  most  points  to 
project  from. 

After  the  views  are  decided  upon,  next  draw  the  center 
lines.  Then  the  sketch  continues  according  to  the  ideas  of  the 
sketcher. 

The  sketches  are  made  quickly,  a  free  sweep  of  the  hand 
for  the  lines  and  a  rapid  proportioning  by  eye  of  the  parts. 
After  the  sketches  are  completed,  the  arrow-points  are  placed 
on  the  sketches  for  the  ends  of  the  dimension  lines.  Cover  the 
sketches  with  these  arrows,  deciding  quickly  what  dimensions 
are  needed.  Then  draw  rapidly  the  dimension  lines,  leaving 
the  spaces  for  the  dimensions.  Then  make  the  measurements 
quickly  and  accurately  and  place  them  on  the  sketch.  In  this 
way  the  work  goes  on  systematically  and  quickly.  After 
completing  the  sketch,  go  over  it  with  the  idea  of  noting 
whether  the  object  could  be  constructed  from  the  notes  taken 
and  the  sketch  made.  Write  on  the  sketch  the  kinds  of  metals 
used  in  the  different  parts,  unless  these  are  shown  by  the 
symbolic  hatching.  Note  if  any  of  the  bolts  or  nuts  differ 
from  the  standard.  Note  what  parts  of  the  object  are  finished, 
and  so  state  on  the  sketch.  If  the  object  is  finished  all  over, 
note  on  the  sketch,  "  Finished  all  over." 

If  a  complicated  machine  is  to  be  sketched,  first  make  a 
free-hand  sketch  of  the  general  outline,  omitting  all  lesser 
details,  but  take  special  care  to  get  the  exact  positions  of  the 
principal  centers  in  all  views.  After  the  general  view  is 
sketched,  the  details  may  be  drawn  one  by  one. 

The  sketches  must  not  be  overcrowded  with  details. 

From  the  dimensioned  sketches  the  scale  drawings  are 
made.  The  scale  of  the  drawing  is  decided  upon,  bearing  in 
mind  a  correct  and  neat  arrangement  of  the  required  views  and 
the  space  for  the  legend. 

Fig.  83  is  a  sample  of  sketching  when  the  lined  paper  is 
used.  It  is  seen  that  two  views,  part  of  one  in  section,  are  all 


GENERAL   DIRECTIONS. 


101 


that  are  needed  for  a  thorough  representation  of  the  object 
The  section  shows  the  material  to  be  cast  iron. 


FIG.  83. 

Plan  of  Procedure  in  Making  a  Drawing. — After  the 
paper  is  stretched  or  tacked  on  the  board  and  is  ready  for  use, 
the  following  is  the  sequence  of  the  different  operations  in 
making  the  drawing  and  blue-print  (if  required). 

1.  Examine  the  object  to  be  drawn,  and  decide  what  views 
are  necessary  so  that  it  may  be  properly  represented. 

2.  Make  dimensioned  sketches. 

3.  Center  the  drawing-paper. 

4.  Mark  the  working,  border,  and  cutting  lines  in  pencil. 

5.  Decide  on  the  scale  to  be  used. 

6.  Establish  the  positions   of  the   center  lines  and  pencil 
them  in  carefully.      (Special  directions  are  given  for  the  first 


102  MECHANICAL  DRAWING. 

drawings  or  sheets,  so  that  from  this  point  the  methods  may 
vary  slightly;  but  the  same  general  plan  is  followed.) 

7.  Inspection  of  the  drawing. 

8.  Pencil  the  drawing. 

9.  Inspection. 

10.  Ink  the  drawing  in  black  ink:  no  sections,  no  tinting, 
no  shade  lines. 

11.  Inspection. 

12.  Tint  or  line  shade,  if  required. 

13.  Inspection. 

14.  Draw  center  lines. 

15.  Draw  extension  and  dimension  lines. 

1 6.  Make  the  dimension  figures  and  arrows. 

17.  Inspection. 

1 8.  Hatch  sections. 

19.  Inspection. 

20.  Draw  shade  lines. 

21.  Inspection. 

22.  Make  the  legends  and  other  lettering. 

23.  Draw  the  border  lines. 

24.  Clean  the  paper. 

25.  Inspection. 

26.  Trace  drawing.      (If  required.) 

27.  Inspection  of  tracing. 

28.  Remove  and  trim  tracing,  and  cut  the  drawing  from  the 
board. 

29.  Make  blue-prints. 

30.  Stretch  or  tack  paper  for  the  next  drawing. 
Remarks  on  the  above:    Before  beginning  any  operation, 

read  the  remarks  under  that  head. 

Pencilling  the  Drawings. — Read  carefully  the  remarks 
under  "  Pencils." 

Note  carefully  the  remarks  under  "  Center  Lines"  and 
carefully  make  all  measurements  from  them  as  far  as  possible. 

Lay  off  first  all  center  lines  for  portions  of  drawings. 


GENERAL  DIRECTIONS.  IO3 

When  straight  lines  are  joined  by  arcs  in  pencil-work, 
the  straight  lines  are  generally  drawn  first  and  centers  of 
the  arcs  found  and  the  arcs  drawn  so  as  to  be  tangent  to 
the  lines.  The  methods  given  in  Geometry  generally  cover 
all  cases. 

When  inking,  the  reverse  method  is  followed,  as  the 
centers  are  already  found;  these  centers  should  be  made  dis- 
tinct in  the  pencilling,  so  that  they  may  be  readily  found  when 
inking. 

Make  no  shade  lines  in  pencil-work. 

Do  no  hatching  in  pencil-work. 

When  a  large  number  of  lines  radiate  from  a  point,  draw 
the  outer  lines  to  the  point  and  stop  all  the  others  at  a  distance 
of  from  J"  to  \"  away. 

Leave  no  centers  to  be  found  when  inking,  and  leave  no 
lines  to  be  "  faired."  The  pencil-work  must  be  complete 
except  for  shade  lines,  hatching,  dimensions,  and  tinting. 

Plan  of  Procedure  in  Inking. — Ink  all  the  arcs  on  the 
board  first,  beginning  with  the  largest ;  then  ink  all  the  irreg- 
ular curve  lines;  then  the  straight  lines.  Always  draw  the 
straight  lines  from  the  curves  if  possible — never  towards 
them. 

After  finishing  the  arcs  and  irregular  curves,  use  the  tri- 
angles, beginning  at  the  top  of  the  board.  Place  the  T  square 
so  that  the  triangle  laid  in  place  will  reach  just  above  the 
highest  lines  on  the  board.  Beginning  at  the  left  sweep  across 
the  board  with  the  triangle  and  draw  the  vertical  lines  found 
at  any  part  of  any  one  of  the  drawings  or  views.  Then  lower 
the  T  square  and  again  sweep  across  with  the  triangle ;  and  so 
on  until  all  the  vertical  lines  on  the  board  are  completed. 

The  horizontal  lines  are  drawn  by  means  of  the  T  square, 
beginning  at  the  top  of  the  board  and  sweeping  the  T  square 
from  top  to  bottom,  drawing  lines  as  they  appear  above  the 
T  square  at  any  part  of  the  board. 

Read  carefully  the  remarks  under  "R.  L.  Pen." 


104  MECHANICAL  DRAWING. 

If  the  drawing  is  to  be  tinted  or  covered  with  line  shad- 
ing, note  carefully  the  remarks  under  these  headings,  and 
take  care  not  to  draw  a  heavy  line  until  the  drawing  has 
been  washed. 

In  shading  the  circles,  follow  the  method  as  in  draw- 
ing them;  shade  the  large  ones  first,  then  the  smaller  ones, 
etc. 

Read  carefully  the  remarks  under  "  Shade  Lines." 

General  Remarks. — Note  always  and  continually  the  direc- 
tion from  which  the  light  should  come. 

Keep  the  instruments  clean.  Clean  them  at  once 'when 
through  using  them. 

Keep  the  instruments  not  in  use  off  the  drawing-board. 

Keep  the  paper  clean. 

Come  to  the  drawing-room  with  clean  hands,  and  clean 
them  often  while  drawing,  if  necessary. 

Cover  the  portions  of  the  drawing  not  being  worked 
upon  with  paper  or  cloth  to  keep  them  clean  and  the 
lines  clear. 

Never  do  free-hand  work  that  may  be  done  with  the  instru- 
ments. Even  "  breaks  "  and  "  tails  "  may  be  made  best  with 
instruments. 

The  excellence  of  the  work  is  of  far  more  importance  than 
speed.  It  is  better  to  make  one  good  drawing  than  a  dozen 
poor  ones.  Speed  combined  with  excellent  work  is  the  object 
aimed  at,  but  the  speed  must  come  last. 

Pens  that  are  dull,  or  instruments  requiring  repairs,  may  be 
turned  in  to  the  desk.  It  is  advisable,  however,  for  all  to  learn 
to  sharpen  their  own  pens. 

When  compass  pens  require  sharpening,  turn  in  the  whole 
instrument,  so  the  sharpening  may  be  tested. 

Pens  that  are  found  to  be  soft  may  be  turned  in  for  retem- 
pering. 

Attach  to  the  instruments  turned  in  a  slip  of  paper  giving 
name,  class,  and  repairs  needed. 


GENERAL  DIRECTIONS.  105 

Write  the  names  clearly  on  the  covering  cloths  and  on  all 
triangular  scales,  irregular  curves,  etc. 

Write  the  names  clearly  in  ink  on  the  N.  W.  corner  of  the 
drawing-paper  outside  the  border  line. 

Bring  all  models  to  the  middle  of  the  room  at  the  end  of 
the  period. 


FIRST  DRAWINGS. 


THESE  consist  of  two  sheets.  Sheet  I  is  for  the  purpose  of 
teaching  the  use  of  the  instruments;  Sheet  II  is  a  study  of  Pro- 
jection and  Working  Drawings.  In  Sheet  I  there  are  twenty- 
one  figures.  Each  figure  represents  a  block  raised  above  the 
drawing-board.  Some  of  the  figures  show  lines  drawn  on  the 
upper  surface  of  the  blocks,  and  some  show  other  figures  resting 
on  the  top  of  the  original  one.  The  figures  in  this  sheet  are  all 
"  Plans."  The  remaining  portion  of  the  sheet  is  for  the 
"  Legend." 

Figs.  A  to  J  consist  of  straight  lines  only.  The  attempt  is 
made  to  bring  into  these  figures  all  kinds  of  straight-line 
work. 

Figs.  K  to  V  consist  of  arcs,  combinations  of  arcs  and  straight 
lines,  combinations  of  arcs  with  other  arcs  and  with  irregular 
curves,  irregular  curves.  The  attempt  is  made  to  bring  into 
these  figures  all  kinds  of  curved-line  work. 


M 


eH 


N 


T 


D 


r 


K 


P 


Q 


GENERAL  VIEW  OF  SHEET  I. 


106 


FIRST    DRAWINGS.  107 

Sheet  II  consists  of  drawings  of  brass  models.  Several 
views  are  made  of  each  model  and  the  points  are  all  projected. 
The  models  are  -cut  across  in  certain  planes  and  are  pinned 
together.  They  may  be  separated  at  the  planes,  and  sections 
studied  and  drawn.  They  are  then  hatched  with  Standard 
Hatching. 

The  figure  on  p.  105  shows  the  dimensions  of  the  Working, 
Border,  and  Cutting  Lines,  and  the  dimensions  of  the  figures 
of  Sheet  I. 

SHEET    I. 

As  stated  under  "Working,  Border,  and  Cutting  Lines,'* 
center  the  drawing-paper  and  draw  the  lines.  Measure  once 
only  for  these  lines  and  carry  the  lines  across  from  these 
measurements.  The  T  square  and  triangles  are  depended  upon 
for  the  rectitude  of  the  lines. 

On  the  first  ruled  page  of  the  sketch-book  make  a  sketch 
of  the  general  view  of  the  sheet,  placing  there  the  dimensions 
of  the  bounding  lines  of  the  paper  and  of  the  figures  of  the 
sheet.  Full  directions  should  be  given  with  the  sketch  so  that 
the  outlines  may  be  drawn  from  it.  This  should  occupy  only 
about  one-fourth  of  a  page  in  the  sketch-book,  leaving  room 
for  some  of  the  figures. 

Mark  off  to  "  full-size  scale  "  the  boundaries  of  the  different 
figures  of  the  sheet.  Measure  along  the  center  lines  and  draw 
carefully.  One  measurement  only  should  be  made  for  each 
line,  and  the  lines  should  be  carried  across  the  board. 

The  outer  lines  of  the  figures  coincide  with  the  working 
lines  of  the  paper. 

Sketch  each  figure  in  the  sketch-book  before  putting  it  on 
the  drawing-board.  The  text-book  is  then  kept  closed  and 
the  work  is  done  entirely  from  the  sketch-book.  The  text- 
book is  to  be  used  only  for  correcting  the  sketch.  Sketch  a 
row  of  figures  at  a  time  and  then  draw  all  the  figures  of  that 
row. 


108  MECHANICAL  DRAWING. 

Pencil-work. — Place  Fig.  A  in  the  upper  left-hand  corner; 
continue  on  to  the  right  along  the  upper  row  of  figures;  begin 
again  at  the  left  hand  of  the  second  row  and  continue  as 
before  to  the  right;  leave  the  legend  until  all  the  figures  are 
inked. 

Finish  completely  in  pencil  all  the  figures  of  a  horizontal  row 
before  inking  any  figure. 

Pencil-lines  cannot  be  made  too  fine,  provided  they  are 
clear-cut  and  distinct.  See  notes  under  "  Pencils  and  Pencil- 
ling." 

When  the  pencil-work  of  all  the  figures  of  a  row  is  com- 
pleted, the  drawing  must  be  inspected  before  the  next  step  is 
begun. 

Put  no  dimensions  in  pencil  on  the  drawing. 

When  a  row  of  figures  is  completed  cover  it  with  paper. 

Ink-work. — In  inking,  do  not  make  too  fine  lines.  Follow 
the  directions  under  "  Use  of  the  R.  L.  Pen." 

For  this  sheet  disregard  the  general  instructions  for  inking 
drawings,  and  ink  each  figure  in  its  order  as  pencilled,  but  ink 
none  until  all  the  pencil-work  of  a  row  is  completed. 

When  inking  the  drawing,  make  all  the  lines  of  the  same 
figure  and  of  the  same  type  of  the  same  width.  Set  the  pen 
before  drawing  the  first  line,  and  draw  a  sample  line  on  the 
margin  of  the  paper  beyond  the  cutting  line,  taking  care  to 
draw  this  line  by  guiding  the  pen  against  the  T  square  or  tri- 
angle. Often  test  the  pen  by  drawing  a  line  near  the  sample 
line  for  comparison. 

When  all  the  figures  of  a  row  are  inked,  the  drawing  must  be 
inspected  before  the  next  step  is  begun. 

After  all  the  figures  of  the  sheet  are  inked,  draw  the  shade  or 
relief  lines  on  the  right-hand  and  lower  sides  of  the  figures  and 
on  the  other  parts  as  required.  Make  these  lines  about  four 
times  as  heavy  as  the  other  parts  of  the  drawing.  These  lines 
are  drawn  over  the  lines  previously  drawn,  but  the  extra  width 
of  line  is  outside  of  the  original  lines.  All  these  shade  lines 


FIRST  DRAWINGS. 


109 


are  of  the  same  width  throughout  the  sheet,  and  they  must  not 
be  too  heavy.  The  pen  is  opened  the  right  amount,  and  the 
line  made  with  one  sweep. 

In  drawing  these  shade  lines,  draw  the  vertical  ones  first. 

Another  inspection  of  the  drawing  is  made  after  the  shade 
lines  are  completed. 

After  the  shade  lines  are  inspected,  the  legend  is  placed  in 
the  space  reserved  for  it.  Lines  are  drawn  in  pencil  at  the 
proper  distances  apart  and  the  block  letters  are  laid  off.  Care 
must  be  taken  to  calculate  the  spaces  occupied  by  the  letters 
so  as  to  have  the  letters  central  in  the  space  left  for  the  pur- 
pose. See  notes  under  "  Lettering. " 

The  lettering  of  the  free-hand  type  is  next  made,  the  name 
written,  and  then  an  inspection  follows.  Scales  are  marked 
as  stated  under  "  Triangular  Scale." 

After  this  inspection,  the  border  lines  are  drawn  and  the 
drawing  cleaned. 

A  final  inspection  follows,  and  then  the  drawing  is  cut  from 
the  board.  Paper  is  stretched  or  tacked  for  the  next  drawing. 


SHEET  I.    FIG.  A. 

Scale,  full  size.     (Use  32  scale.) 

Horizontal  full  and  broken  lines. 


no 


MECHANICAL    DRAWING. 


T  square;  triangular  scale;  full  and  broken  lines,  pencil  and 
ink. 

Pencil-work. — Measure  off  the  vertical  distances  as  given 
and  mark  the  points  with  the  bow  spacer  or  pricker.  Draw 
lines  across  at  all  marked  points. 

Sweep  the  lines  across  in  pencil  from  left  to  right,  not  at- 
tempting to  begin  or  stop  the  lines  exactly  at  the  boundary  lines. 
%  Ink-work. — The  lines  are  alternately  full  and  broken  lines  of 
standard  width.  Each  line  must  be  clear,  the  nibs  of  the  pen 
cutting  sharply.  The  endeavor  is  to  make  the  full  lines  exactly 
alike,  equal  in  width  and  distinctness,  and  the  broken  lines  as 
much  alike  as  possible,  the  dashes  and  spaces  the  same  through- 
out. Begin  the  lines  firmly,  and  carry  them  on  with  an  even 
pressure,  and  stop  them  exactly  at  the  boundary  line. 

Do  not  draw  the  dimension  lines  until  all  the  figures  of  the 
row  are  completed.  See  notes  under  "  Dimension  Lines." 


SHEET  I.    FIG.  B. 

Scale,  3"  =  i  foot,  or  one-fourth  size. 

Vertical  heavy  lines. 

T  square;    triangular  scale;    triangle;    full  lines,  of  varying 
widths  when  inked. 


FIRST   DRAWINGS.  Ill 

Pencil-work. — From  one  of  the  top  corners  lay  off  hori- 
zontally the  following  distances,  each  distance  measured  from 
the  corner:  i";  2*";  3!";  tf";  6J";  7*";  9*";  "i"- 

Draw  a  horizontal  center  line  and  vertical  lines  through 
each  of  the  points  marked,  also  a  line  J"  above  the  lower 
boundary. 

Ink-work. — Draw  the  boundary  lines  and  the  lines  through 
the  marked  points.  These  lines  are  standard  lines.  Make  the 
upper  halves  of  the  lines  of  increasing  width,  beginning  at  the 
left  with  very  fine  lines  and  increasing  the  width  slightly  for 
each  new  line.  Place  the  extra  width  of  the  lines  entirely 
beyond  the  original  lines  from  the  original  point  of  measure- 
ment. 

Do  not  continue  the  heavy  lines  quite  to  the  top  line,  as 
it  is  difficult  to  carry  a  solid  heavy  line  sharply  to  the  end. 
After  all  the  heavy  lines  are  drawn,  with  the  T  square  as  a 
guide  fill  in  the  short  spaces  left  with  the  R.  L.  pen  and  a  fine 
opening. 

Stop  the  lower  heavy  lines  at  a  distance  of  one-half  inch  from 
the  bottom.  Draw  the  first  five  lines  from  the  left  like  those  above. 
Beginning  with  the  sixth  line  from  the  left,  draw  lines  as  wide  as 
for  the  upper  half  of  the  figure,  but  leave  a  narrow  central  strip 
of  white. 

These  heavy  lines  will  have  to  be  squared  at  the  ends  by 
using  the  R.  L.  pen  along  the  T  square. 

The  right-hand  and  lower  boundaries  of  the  figure  are 
shaded. 

The  center  line  is  drawn,  but  not  the  line  -J-"  above  the  lower 
boundary. 


112 


MECHANICAL    DRAWING. 


SHEET  I.     FIG.  C. 

Scale,  2"  =  i  foot,  or  one-sixth  size. 

45°  triangle. 

T  square;  triangular  scale;  triangle;  full  lines,  of  varying 
widths  when  inked. 

Pencil-work. — Draw  the  diagonals.  From  the  N.  W.  and 
S.  E.  corners  of  the  figure  measure  the  following  distances  on 
the  diagonal  towards  the  center,  each  distance  measured  from 
the  corners:  i";  f";  ij";  2*";  3J";  5i";  f'\  9">  "V-  The 
remaining  distances  are  each  i  j-",  which  is  a  check. 

Through  these  marked  points  draw  lines  parallel  to  the 
other  diagonal  of  the  figure. 

Ink-work. — Draw  the  boundaries  of  the  figure  as  standard 
lines  and  the  lines  through  the  marked  points  with  a  fine  pen. 
Beginning  with  the  lines  nearest  the  corners  make  half  of  each 
successive  line  heavier  than  the  preceding  in  about  the  propor- 
tion of  Fig.  B. 

The  two  lines  nearest  to  the  center  are  made  heavy  all  the 
way  across.  The  added  width  of  the  lines  is  towards  the 
center. 

The  diagonal  lines   are  drawn  as  construction  lines.     See 


FIRST    DRAWING. 


page    164,     "  Lines    to    be    used    in    Drawings,"   at    end  of 
book. 


SHEET  I.    FIG.  D. 

Scale,  full  size. 

45°  triangle. 

T  square;  45°  triangle;  full  lines  in  pencil  and  ink;  shade 
lines. 

The  figure  represents  blocks  resting  centrally  on  each 
other,  the  smallest  on  top. 

Pencil-work. — Center  the  figure  and  draw  as  shown,  using 
only  the  T  square  and  the  45°  triangle. 

The  checks  on  the  work  are  the  inscribed  circles,  as 
shown. 

Ink-work. — The  lines  are  all  standard  lines. 

The  construction  and  check  lines  are  drawn. 

The  blocks  are  shaded  according  to  remarks  under  "  Shade 
Lines." 

Carefully  choose  the  proper  width  of  line,  and  do  not 
change  the  pen  when  shading. 


MECHANICAL   DRAWING. 


SHEET  I.    FIG.  E. 

Scale,  f  "=  i  foot,  or  one  thirty-second  size. 

60°  triangle. 

T  square;  triangular  scale;  triangles;  full  lines  of  standard 
width,  pencil  and  ink;  shade  lines. 

The  figure  represents  blocks  resting  centrally  on  each 
other,  the  smallest  on  top. 

Pencil-work. — Center  the  figure  with  the  45°  triangle  laid 
along  the  T  square.  With  the  60°  triangle  laid  along  the  T 
square  draw  lines  making  angles  of  60°  with  the  horizontal 
through  the  center  of  figure. 

From  the  extremities  of  the  horizontal  center  line  draw 
lines  making  angles  of  60°  with  the  horizontal,  and  extend  them 
to  cut  the  lines  last  drawn.  Through  these  intersections  draw 
horizontal  lines.  This  forms  a  hexagon. 

Through  the  central  point  of  the  figure  draw  a  line  at  30° 
with  the  horizontal,  and  extend  it  to  cut  one  side  of  the 
hexagon.  This  line  will  be  at  right  angles  to  the  side  of  the 
hexagon.  Beginning  at  the  side  of  the  hexagon,  measure  to 
scale  towards  the  center  of  figure  along  the  line  last  drawn  the 
following  distances,  each  distance  measured  from  the  side  of 
the  hexagon:  2" ;  4";  7"',  n";  16";  2.1";  2ft.  5";  3  ft.  i". 


FIRST  DRAWINGS. 


Through  these  points  draw  lines  parallel  to  the  side  of  the 
hexagon  from  which  the  distances  were  measured.  Carry 
these  lines  around  the  figure. 

They  make  a  number  of  hexagons  within  the  original 
hexagon. 

Portions  of  circles  are  drawn  with  the  bow  spacers  as  far 
as  they  can  be  used,  and  after  that  with  the  compasses  through 
the  extreme  points  of  each  hexagon,  as  a  check. 

The  center  of  figure  is  the  center  from  which  these  circles 
are  drawn. 

Ink-work. — Ink  with  standard  lines  the  boundaries  of  the 
figure  and  the  hexagonal  blocks.  Ink  center  lines  and  diago- 
nals of  hexagons  only. 

Place  shade  lines  on  the  blocks.  Take  care  that  the  heavy 
portion  is  outside  the  original  line. 


SHEET  I.     FIG.  F. 

Scale,  i"=i  foot,  or  one-twelfth  size. 

45°  triangle. 

T  square;    triangular  scale;    45°  triangle;    full  lines,  pencil 
and  ink;    shade  lines. 

The  figure  represents  several  45°  triangles. 


n6 


MECHANICAL    DRAWING. 


Pencil-work. — Center  the  figure  and  draw  the  vertical  center 
line  and  the  diagonals.  Draw  the  triangles  as  shown.  The 
distances  between  the  outer  edges  and  the  openings  in  the  triangles 
is  2\"  to  the  given  scale. 

Checks  for  the  work  are  circles  drawn  with  the  center  of 
figure  as  a  center  and  through  the  corresponding  points  of  the 
triangles. 

Ink-work. — Use  standard  lines  and  ink  no  construction  or 
check  lines.  Extend  both  center  lines  beyond  the  figure.  Shade 
the  proper  edges. 


SHEET  I.    FIG.  G. 

Scale,  full  size. 

45°  and  60°  triangles. 

T  square;  triangles;  full  lines  of  varying  widths,  pencil  and 
ink. 

Pencil-work. — Draw  the  diagonals.  With  the  45°  triangle 
in  position  on  the  T  square  and  the  60°  triangle  resting  against 
the  45°  triangle,  draw  the  figure  for  all  four  quandrants.  The 
checks  for  accuracy  are  circles  drawn  with  the  center  of  figure 
as  the  center  and  radii  for  corresponding  points. 


FIRST    DRAWINGS. 


117 


Ink-work. — Large  equilateral  triangles  and  lines  within,  stand- 
ard lines:    small  ones,  fine  lines. 

Ink  center  lines  and  diagonals  but  not  check  circles. 


SHEET  I.     FIG.  H. 

Scale,  4"=!  foot,  or  one-third  size. 

60°  triangle. 

T  square;  triangular  scale;  60°  triangle;  full  lines  in  pencil, 
full  and  broken  lines  in  ink. 

Pencil-work. — All  lines  are  full  lines. 

Using  the  scale  given  mark  off  the  line  AB  into  lengths 
of  i",  and  the  lines  AC  and  BD  into  lengths  as  follows: 
AE  =  BG=CF  =  DH=il,".  Divide  these  lines  into  spaces  \" 
long.  Divide  the  line  GH  into  spaces  \"  long. 

From  the  division  of  AB  draw  lines  at  angles  of  30°  with  the 
T  square. 

The  triangles  are  laid  along  the  T  square,  and  lines  are 
drawn  from  left  to  right  always. 

The  vertical  center  line  JK  is  a  check  on  the  work. 

From  the  divisions  of  AE  and  FC,  draw  lines  at  angles  of 


n8 


MECHANICAL    DRAWING. 


30°  with  the  T  square.  From  the  divisions  of  GH  draw  lines 
at  angles  of  60°  with  the  T  square. 

The  horizontal  center  line  LM  is  a  check,  as  all  the  inter- 
sections should  be  on  that  line. 

Ink-work. — Draw  full  lines  as  fine  as  the  pen  will  maintain 
from  the  divisions  of  AE  and  FC  to  the  horizontal  center  line. 

Draw  full  lines  from  the  divisions  of  GH  to  the  horizontal 
center  line,  the  lines  to  be  of  the  same  width  as  the  lines  previously 
drawn — noting  that  the  lines  stop  where  they  come  in  contact 
with  the  previously  completed  full  lines. 

Draw  standard  lines  from  the  divisions  of  AB  to  the  vertical 
center  line. 

Draw  the  vertical  and  horizontal  center  lines. 


SHEET  I.     FIG.  I. 

Scale,  full  size. 

Bow  spacers. 

triangle;    bow  spacers; 


full  lines  in  pencil, 


T  square;    45' 
full  and  broken  lines  in  ink. 

Pencil-work. — Draw    the    diagonals.     These    should    check 
exactly  with  the  45°  triangle  laid  along  the  T  square. 

With  the  bow  spacers,  space  by  trial  (see  "  Bow   Spacers  ") 
each  of  the  half-diagonals  AO  and  OD  into  nine  parts,  and  draw 


FIRST  DRAWINGS,  119 

full  lines  through  each  point  parallel  to  the  other  diagonal,  using 
the  45°  triangle  sliding  along  the  T  square.  Draw  from  the  S.  W. 
point  and  begin  with  that  nearest  A. 

Do  not  take  time  to  begin  and  stop  the  lines  at  the  bound- 
aries. 

"-"      C-.  •'  " 

With  the  bow  spacers  divide  each  space  of  OD  into  three 
parts  and  draw  full  lines  as  before. 

F  is  at  five  of  the  original  spaces  from  the  center. 

Divide  the  spaces  FD  into  two  parts  with  the  bow  spacers 
and  draw  lines  as  before. 

Note  that  in  this  figure  the  lines  that  are  to  be  broken  lines 
when  inked  are  not  drawn  broken  in  the  pencil-work. 

Ink-work. — Draw  the  lines  alternately  full  and  broken  lines, 
varying  the  lengths  of  the  dashes  from  \"  long  for  the  lines  farthest 
apart  to  -f$"  long  for  those  nearest  together. 

Ink  diagonal  construction  line. 


SHEET  I.    FIG.  J. 

Scale,  full  size. 

Section :     Hatching. 


120  MECHANICAL   DRAWING, 

T  square;  triangles;  bow  spacers;  full  lines,  pencil  and 
ink ;  shade  lines ;  hatching. 

The  figure  represents  a  horizontal  section  through  a  piece 
of  cast  iron,  the  iron  resting  on  the  lower  block. 

Pencil-work. — Divide  one  top  and  one  side  boundary  line 
into  six  parts  each  by  drawing  lines  from  a  corner  at  an  angle 
and  using  the  bow  spacers  and  a  different  spacing  length  for 
each. 

Draw  the  horizontal  and  vertical  lines,  running  them 
entirely  across  the  figure.  Do  not  hatch  in  pencil. 

Ink-work, — Draw  the  figure  in  standard  lines. 

Begin  at  the  N.  W.  corner  and  hatch  the  figure  with  lines 
at  an  angle  of  45°,  from  S.  W.  to  N.  E. 

The  line  used  for  hatching  is  not  the  finest  the  pen  may 
make,  but  is  as  fine  a  line  as  can  be  depended  upon.  Do  not 
fail  to  make  every  line  of  the  hatching  just  as  distinct  as  if  it 
were  a  line  of  the  figure. 

When  a  line  of  the  hatching  is  begun  and  ends  at  a  space, 
the  same  line  is  continued  beyond  the  space  if  it  would  cut  the 
figure  farther  on. 

Shade  the  figure  according  to  remarks  under  "Shade 
Lines." 

Refer  to  remarks  under  *  *  Hatching. ' ' 

Ink  center  and  construction  lines. 


FIRST   DRAWINGS. 


121 


SHEET  I.     FIG.  K. 

Scale,  full  size. 

Compass. 

i; 

T  square;  triangles;  compasses;  same  radius  for  all  circles; 
full  lines  in  pencil  and  ink;  varying  widths  of  lines  in  ink- work. 
See  remarks  under  "  Compasses." 

Pencil-work. — Center  the  figure  by  drawing  diagonals.  Use 
the  center  of  figure  as  a  center  and  a  radius  to  the  middle  point 
of  one  side  and  draw  a  circle.  Take  care  to  properly  bend  the 
knees  of  the  compass.  This  circle  should  exactly  touch  the 
boundaries  at  the  middle  points. 

Begin  at  the  middle  point  of  the  left-hand  boundary  line 
and  with  the  same  radius  as  before  draw  an  arc  ending  at  the 
first  circle  drawn.  Use  the  point  where  this  arc  cuts  the  first 
circle  drawn  as  a  center  and  draw  another  arc;  and  so  on 
around  until  the  last  arc  drawn  passes  through  the  first  center 
used  on  the  left.  Every  one  of  these  arcs  should  pass  exactly 
through  the  center  of  figure. 

From  each  of  the  corners  of  the  figure  draw  arcs.  These 
should  pass  exactly  through  the  middle  points  of  the  sides. 


122 


MECHANICAL    DRAWING. 


Ink-work. — Set  the  pen  for  the  first  circle  and  first  set  of 
arcs  drawn.  Make  this  a  fair  line — not  as  fine  as  the  pen  will 
make — and  draw  a  sample  line  on  the  margin  of  the  paper 
where  others  may  be  compared  with  it  at  will.  Draw  the  first 
circle.  Draw  the  next  set  of  arcs  until  they  end  at  the  first  circle. 

Set  the  pen  for  the  other  arcs,  making  the  sample  line  the 
standard  line.  Draw  the  arcs  that  have  the  corners  as  centers, 
extending  them  to  the  boundaries. 

Draw  the  construction  and  center  lines. 


SHEET  I.     FIG.  L. 

Scale,  4"=  i  foot. 

Compasses,  bow,  pencil,  and  pen. 

T  square;  triangles;  triangular  scale;  compasses;  bow 
pencil  and  pen;  full  lines,  pencil  and  ink,  varying  widths  in  ink. 

Pencil-work. — Center  the  figure.  Draw  the  center  lines. 
From  the  middle  point  of  the  top  boundary  line  measure  down- 
ward the  following  dimensions:  J";  f ';  4";  if";  2j";  3!"; 
4j".  The  remaining  distance  to  the  center  is  f ". 

Using  the  bow  pencil  (see  notes  under  "  Bow  Pencil ") 
with  the  center  of  figure  as  a  center  draw  circles  through  each 


FIRST    DRAWINGS. 


123 


of  the  points  marked,  until  the  circles  became  so  large  that  the 
compasses  must  be  used. 

Ink-work. — Using  the  bow  pen  (see  notes  under  "  Bow 
Pen"),  draw  the  smaller  circles.  Use  compass  for  the  larger 
ones.  Make  the  inner  one  a  fine  line  and  the  others  gradually 
increasing  in  width  to  the  outer  one,  the  one  tangent  to  the 
boundaries.  Place  the  extra  width  of  line  on  either  side  of  the 
pencil-line  but  do  not  make  the  outer  circle  pass  outside  the 
boundaries. 

Draw  the  diagonals  and  the  horizontal  and  vertical  center 
lines. 


SHEET  I.     FIG.  M. 

Scale,  full  size. 

Bow  pencil  and  pen. 

T  square ;  triangles ;  triangular  scale ;  bow  pencil  and  pen ; 
full  lines  in  pencil,  full  and  broken  lines  in  ink. 

Pencil-work. — Draw  the  center  lines.  Divide  each  of  these 
lines  into  six  parts  by  any  method  and  draw  vertical  and  hori- 
zontal lines  through  these  divisions.  Draw  arcs  as  shown, 
using  a  radius  equal  to  the  length  of  the  diagonal  of  two 
adjacent  squares.  Take  time  in  getting  the  exact  radius  by 


124 


MECHANICAL    DRAWING. 


trial   at   several   points   and  do  not  change  this   radius  while 
drawing  the  arcs. 

Ink-work.  —  Set  the  pen  as  exactly  to  the  correct  radius  as 
possible  and  do  not  change  the  setting  while  drawing  the  lines. 
Make  the  lines  quite  fine.  Draw  every  other  pair  of  arcs  full 
lines  and  the  remaining  ones  broken  lines  with  dashes  about 


After  all  the  arcs  are  drawn,  go  over  the  top  and  bottom 
rows  of  full  lines,  making  them  standard  lines,  keeping  the 
extra  width  of  line  within  the  boundary  lines. 

Draw  the  vertical  and  horizontal  lines  as  construction 
lines. 


SHEET  I.     FIG.  N. 

Scale,  2"=!  foot. 

Fillets. 

T  square;  triangles;  triangular  scale;  bow  pencil  and  pen; 
full  lines  in  pencil,  full  and  broken  lines  in  ink. 

The  figure  represents  blocks  resting  upon  each  other. 

Pencil-work. — Draw  the  center  lines.  On  the  horizontal 
center  line  measure  from  the  center  to  right  and  left  the  fol- 
lowing dimensions:  ij";  2j";  4J";  6";  ;1";  8J";  9". 


FIRST    DRAWINGS.  125 

On  the  vertical  center  line  measure  from  the  center  up- 
wards and  downwards  the  following  dimensions  :  2j";  4";  5^"; 

6i";  7f":  8i";  9"- 

Construct  rectangles  with  the  use  of  the  T  square  and  tri- 
angles on  the  corresponding  measurements.  Connect  the 
corners  of  the  rectangles  with  small  arcs  or  "  fillets,"  as  fol- 
lows : 

For  the  N.  E.  corners,  use  radii  in  succession,  beginning 
with  the  inner  rectangle,  as  follows  :  J";  i";  ij";  2";  2\"  3"; 

si". 

For  the  N.  W.  corners,  as  before,  use  the  following  radii  : 
f";  ij";  if";  2\";  2}";  31";  3f '. 

For  the  S.  W.  corners,  as  before,  use  the  following  radii  : 
I";  ij";  2";  2*";  3";  3*";  4"- 

For  the  S.  E.  corners,  as   before,  use  the  following  radii  : 

ii";  i4";  2i";  2*";  si";  3*";  4i". 

In  drawing  these  fillets,  from  the  corner  of  the  rectangle 
swing  an  arc  around  of  the  correct  length  to  cut  the  adjacent 
sides  of  the  rectangle.  From  these  points  swing  arcs  of  the 
same  radius  to  meet  each  other.  These  last  points  are  the 
centers  from  which  to  draw  the  fillets. 

Many  draftsmen  of  experience  do  not  take  the  trouble  to 
define  these  centers,  but  find  them  rapidly  and  accurately  by 
trial. 

Carefully  draw  all  these  fillets  with  the  bow  pencil.  Mark 
the  centers  clearly.  Swing  the  arcs  beyond  the  points  of  tan- 
gency,  as  it  is  impossible  to  determine  that  the  arc  is  exactly 
right  if  it  stops  on  the  line. 

Ink-work. — Ink  all  the  fillets  first  with  standard  lines. 

In  inking  the  straight  lines,  carefully  set  the  bow  pen  for 
the  first  line  to  agree  with  the  line  of  the  fillets.  Draw  the 
vertical  lines  first  one  after  the  other,  beginning  at  the  left. 
Always  draw  from  the  fillet  at  the  left  hand  towards  the  one 
at  the  right  and  stop  the  line  near  the  fillet  and  draw  a  line 
from  the  right-hand  fillet  to  meet  the  previously  drawn  line. 


126 


MECHANICAL    DRAWING. 


This  allows  of  a  slight  moving  of  the  pen  from  or  towards  the 
triangle  or  T  square  to  meet  the  other  line  fairly.  This  case 
of  drawing  a  straight  line  to  meet  two  curves  is  the  only  one 
where  it  is  advisable  to  break  the  general  rule  of  drawing  from 
left  to  right. 

Shade  each  block. 

Draw  the  center  lines. 


SHEET  I.  FIG.  O. 

Scale,  £"=i  foot. 

Two  arcs  and  straight  line  joining  them. 

T  square;  triangles;  triangular  scale;  bow  pencil  and  pen; 
connecting  tangents  with  arcs;  full  lines  in  pencil,  full  lines  in 
ink. 

Pencil-work. — Draw  the  center  lines. 

With  centers  on  the  horizontal  center  line,  draw  arcs  tangent 
to  the  side  boundary  lines  at  the  middle  points  with  the  following 
radii:  2  ft.  6J";  2  ft.  3";  21*";  i4J";  8";  2". 

Connect  these  corresponding  arcs  above  and  below  the 
horizontal  center  line  with  straight  lines,  using  the  triangles 


FIRST    DRAWINGS. 


127 


only.  Draw  a  line  away  from  the  left-hand  arc  and  extend  it  to 
near  the  other  arc;  then  break  the  established  rule  of  drawing 
lines  from  left  to  right  and  draw  a  line  away  from  the  right-hand 
arc  to  connect  with  the  line  already  drawn. 

The  T  square  moved  up  and  down  the  board  is  a  check  on 
the  work. 

Ink-work. — Draw  the  arcs  and  tangents  in  full  lines,  making 
the  inner  one  a  fine  line  and  increasing  the  width  of  the  other 
lines  as  the  radii  increase. 

Draw  the  vertical  and  horizontal  center  lines. 


SHEET  I.    FIG.  P. 

Scale,  full  size. 

Protractor,  arcs,  and  straight  lines. 

T  square;  triangles;  triangular  scale,  protractor;  full  lines  in 
pencil,  full  and  broken  lines  in  ink. 

Pencil-work. — From  the  two  bottom  corners  lay  off  upward 
from  the  bottom  line  and  within  the  figure  the  following  angles : 


11°;  18°  30';  27°;  36°  30';  48°;  60°  30';  74°;   88°  30'. 

Join  seven  of  the  corresponding  pairs  of  lines  with  tangential 


128 


MECHANICAL    DRAWIXG. 


arcs  of  the  following  radii  in  succession,  beginning  with  the  lines 
drawn  from  the  smallest  angles:  2";  ij";  ij";  ij";  i";  -f";  i". 
For  the  next  set  of  lines  use  a  radius  that  will  make  the  arc 
tangent  to  the  two  lines  and  to  the  top  boundary  line.  For  the 
last  set  of  lines,  use  a  radius  of  J"  and  draw  arcs  tangent  to  the 
lines  and  to  the  top  boundary  line. 

The  centers  are  found  by  trial. 

Ink-work. — Ink  all  the  arcs  first  and  draw  the  straight  lines 
away  from  the  arcs.  Make  the  lines  all  standard. 

Draw  the  vertical  center  line.  Lay  off  and  figure  dimension 
angles  at  lower  right-hand  corner. 


SHEET  I.    FIG.  Q. 

Scale,  10. 

Tangent  arcs. 

T  square;  triangles;  triangular  scale;  compasses;  bow  pencil 
and  pen;  full  arcs  in  pencil,  full  lines  in  ink. 

Pencil-work. — Center  the  figure  and  draw  center  lines  and 
diagonals,  extending  these  lines  beyond  the  boundaries  of  the 
figure  about  3". 

From  the  center  of  figure  measure  on  one  of  the  center  lines 


FIRST    DRAWINGS. 


129 


in  one  direction   only  the   following1  dimensions:    "50;  "75; 

T//.      -r't'tr'-       •tH'-lf'     O  "o  r*  •        •3"  •      Atf 

I     ,    I  .25,    I   .75,  2  .25,     3,4. 

With  the  bow  pencils  and  compasses,  swing  these  dimen- 
sions around  the  central  point  and  mark  them  on  the  other  side 
of  the  center  line  used  and  on  both  sides  of  the  center  line  not 
first  used. 

With  these  points  as  centers  draw  arcs  tangent  to  the 
adjacent  diagonals,  extending  them  just  enough  beyond  the 
diagonals  to  ensure  their  tangency.  These  radii  are  determined 
by  trial  only. 

The  larger  arcs  meet  the  extensions  of  the  diagonals,  but 
are  drawn  only  within  the  boundaries. 

Checks  for  the  work  are  circles  drawn  with  the  center  of 
figure  as  a  center  and  radii  to  the  points  of  tangency  of  corre- 
sponding arcs  on  the  diagonals. 

Ink-work. — Draw  the  arcs  from  diagonal  to  diagonal  in 
standard  lines. 

Draw  the  center  and  diagonal  lines. 


SH^ET  I.     FIG.  R. 

Scale,  full  size. 

Connecting  arcs. 

T  square;  triangles;  triangular  scale;  bow  pencil  and  pen; 
compasses;    full  lines  in  pencil,  full  and  broken  lines  in  ink. 


130  MECHANICAL   DRAWING. 

Pencil-work. — Center  the  drawing  by  diagonals.  Find  the 
middle  points  of  the  half  diagonals  running  N.  E.  and  S.  W. 
From  the  lower  one  of  these  centers  draw  arcs  with  the  follow- 
ing radii  :  J";  f";  £";  f ';  f". 

From  the  upper  one  of  these  centers  draw  arcs  of  the  fol- 
lowing  radii  :  f ;  i";  f";  i";  f  ". 

Connect  the  arcs  on  the  lower  side,  beginning  with  the 
largest  of  each  set,  by  arcs  with  the  following  radii  in  succes- 
sion :  2";  2Ty';  2\"\  2Tyr;  2j".  These  arcs  are  convex  look- 
ing from  the  top  down. 

Connect  the  first  set  of  arcs  on  the  upper  side,  beginning 
with  the  largest  of  each  set,  by  arcs  with  the  following  radii  in 
succession  :  3^";  3T\";  3f";  SyV';  3i' '•  These  arcs  are  con- 
cave looking  from  the  top  down. 

The  centers  of  these  arcs  are  found  as  follows : 

On  any  line  through  the  center  0',  as  the,  line  00' ',  measure 
off  from  the  arc  drawn  with  o'  as  a  center  the  distance  for  the 
radius  of  the  tangent  circle.  This  gives,  for  instance,  the 
point  a.  On  any  line  through  the  center  0,  as  the  line  oo' 
measure  off  from  the  arc  the  same  distance,  as  the  point  b. 
With  o'  as  a  center  and  radius  o'a,  and  with  o  as  a  center  and 
radius  ob,  strike  arcs  to  meet  each  other.  This  is  the  center 
required,  as  point  e. 

Draftsmen  of  experience  often  find  these  centers  by  trial,  as 
that  method  is  quicker  and  sufficiently  accurate  for  all  practical 
purposes. 

Ink-work.  — Draw  the  larger  arcs  first  with  the  compasses 
and  then  the  smaller  ones  with  the  bow  pen.  This  allows  of 
slight  bending  or  springing  of  the  bow  pen  to  allow  for 
inaccuracies  of  the  work. 

The  lines  are  made  standard  size  and  the  two  inner  sets  of 
lines  are  broken,  with  dashes  about  -J"  long.  Stop  the  inner 
lines  at  the  points  of  meeting.  Shade  the  three  larger 
figures. 

Draw  diagonals  and  one  set  of  construction  lines. 


FIRST  DRAWINGS. 


SHEET  1.     FIG.  S. 

Scale,  full  size. 

Ellipses:  Irregular  curves. 

T  square;    triangles;  triangular  scale;    bow  pencil  and  pen; 
compasses;    irregular  curves;  full  lines  in  pencil  and  ink. 
Pencil-work. — Center  the  figure  and  draw  the  center  lines. 
From  the  center  measure  upwards  the  following  dimensions0. 

i";  i";  ii". 

From  the  center  measure  to  right  or  left  the  following  dimen- 
sions: i";  ij";  ij". 

The  corresponding  horizontal  and  vertical  distances  are 
semiaxes  of  ellipses.  Construct  the  largest  of  the  ellipses  on 
these  axes  extended  to  the  other  sides  of  the  center,  by  the  fol- 
lowing method: 

Draw  AB.  With  O  as  a  center  swing  the  distance  OB  to  the 
point  D.  Take  the  distance  AD  and  measure  it  from  B  to  C. 
Bisect  AC  and  extend  the  bisecting  line  to  meet  the  vertical  axis 
at  E.  With  £  as  a  center  and  a  radius  EB  draw  an  arc  to  right 
and  left  of  B,  extending  it  to  the  line  EK.  With  H  as  a  center 
draw  an  arc  with  HA  as  a  radius;  this  line  will  meet  the  line  of 


132  MECHANICAL    DRAWING. 

the  ellipse  drawn  from  B  with  £  as  a  center,  and  this  method  of 
construction  is  an  approximate  method  of  constructing  an  ellipse. 
If  the  work  is  not  done  with  the  utmost  accuracy,  the  irregular 
curves  must  be  used  to  join  the  arcs  fairly.  See  note  under 
"  Irregular  Curves." 

Construct  the  remaining  ellipses  by  the  following  method: 
From  M  lay  off  the  semiminor  axis,  OAT",  to  the  point  R.  With 
the  length  RP  as  a  radius  describe  arcs  through  N  and  S.  Make 
OT  =  %OR.  With  Tasa  center  draw  an  arc  through  M.  If 
drawn  with  care  this  arc  meets  those  already  drawn. 

Divide  the  horizontal  center  line  into  twelve  equal  parts, 
using  the  triangular  scale. 

On  the  two  outside  lines  next  the  vertical  boundary  lines 
measure  off  from  the  horizontal  center  line,  above  and  below, 
10". 

On  the  next  two  interior  lines  on  each  side  measure  off  in  the 
same  way  nj". 

On  the  next  two  lines  measure  as  before  12". 

On  the  next  two  lines  measure  as  before  nf". 

On  the  next  two  lines  measure  as  before  n^". 

On  the  middle  line  measure  off  as  before  nj". 

See  notes  under  "  Irregular  Curves." 

Through  the  ends  of  the  horizontal  center  lines  and  the  cor- 
responding measurements  draw  a  smooth  curve  with  the  aid  of 
the  irregular  curves.  The  line  is  to  be  tangent  to  the  vertical 
boundary  line  at  the  middle  point. 

Note  that  the  curves  correspond  on  either  side  of  the  center 
lines. 

Ink-work. — Draw  the  arcs  of  the  ellipses  first  and  finish  with 
the  irregular  curves  later,  if  necessary.  Care  is  required  in  car- 
rying the  arcs  just  far  enough  and  not  too  far.  The  lines  are  all 
standard  lines  (shaded  for  ellipses).  Ink  the  irregular  curve  with 
standard  line. 

Draw  center  lines  and  the  construction  lines  of  one-quarter  of 
one  ellipse  drawn  by  each  method. 


FIRST    DRAWINGS. 


133 


SHEET  I.    FIG.  T. 

Scale,  i"=i  foot. 

Heavy  lines  with  narrow  spaces  between. 

T  square ;  triangle ;  triangular  scale ;  bow  pencil  and  pen ; 
compasses;  shade  lines;  full  lines  in  pencil  and  ink. 

The  figure  represents  sections  of  sheet  metal  standing  on 
end.  Where  the  sheets  lap,  a  fine  white  line  is  left,  the  entire 
width  of  this  being  taken  from  one  sheet.  The  ends  of  the 
laps  are  closed,  as  shown. 

Pencil-work. — Use  the  center  of  figure  as  the  center  for  the 
rings  of  metal.  The  radii  of  the  mean  diameters  of  the  rings 
are  as  follows  :  9";  I2f";  i6J". 

The  thicknesses  of  the  sheets,  beginning  with  the  outer 
ones,  are:  if;  i";  J". 

Make  the  joints  for  the  outer  rings  at  the  sides  and  for  the 
next  inner  one  at  top  and  bottom.  Alternate  to  the  innermost 
one. 

The  laps  are  30°  long,  half  on  each  side  of  the  center  line. 

Construct  the  joints  of  plating. 

Ink-work. — Carefully  draw  the  boundaries  of  the  metals 
with  quite  a  fine  opening  of  pen  and  fill  in  with  a  widely  opened 


134  MECHANICAL    DRAWING. 

pen.     Do  not  attempt  to  bring  the  heavy  ink-lines  sharply  to  the 
ends.     Finish  them  off  with  the  triangle  and  R.  L.  pen. 

Draw  center  lines.     Dimension  the  complete  circles,  giving 
diameters.     (See  Dimensions.) 


SHEET  I.    FIG.  U. 

Scale,  2"  =  I  foot. 

Shading  circles :    Hatching. 

T  square ;  triangles ;  triangular  scale ;  compasses ;  bow 
pencil  and  pen ;  shading  circles ;  full  lines  in  pencil  and  ink. 

The  figure  represents  a  section  of  a  hollow  shaft  showing 
beyond  the  section  the  enlarged  portion  for  the  coupling  to  join 
it  to  the  next  shaft.  The  coupling  rests  on  the  rectangular 
block  and  the  shaft  is  vertical. 

Diameter  of  the  outer  circle  of  the  coupling.  .     .  18" 

Diameter  of  the  outside  of  the  shaft 10" 

Diameter  of  the  axial  hole  in  the  shaft 6" 

Diameter  of  the  bolt-circle 14" 

Diameter  of  the  bolts 2" 

Number  of  bolts. .  6 


FIRST    DRAWINGS.  135 

Pencil-work. — Draw  the  center  lines.  The  central  point  is 
the  center  of  the  shaft. 

Ink-work. — After  the  figure  is  completed  with  standard  lines, 
shade  the  circles. 

Draw  the  center  lines  and  the  bolt-circle. 

Dimension  the  drawing  in  accordance  with  the  notes  under 
"  Dimension  Lines."  Mark  the  centers  of  the  bolt-holes  with 
short  full  radial  lines.  These  are  at  right  angles  to  the  bolt- 
circle,  thus  marking  the  centers  properly.  Hatch  the  section 
(wrought  steel).  See  " Standard  Hatching."  Hatch  as  if  for 
cast-iron  and  then  fill  in  the  proper  spaces. 


Legend  and  Lettering  the  Sheet. — The  legend  reads: 
SHEET   I. 

STRAIGHT   AND    CURVED    LINE 
DRAWING. 

Name  [F.  K.  Jones.]        Class  [Fourth  Class.] 
Date    [Dec.  i.  1910.] 

The  space  to  be  used  is  divided  and  the  sizes  of  the  lettering 
arranged  by  each  one  according  to  his  judgment.  "Sheet  I" 
and  "Straight  and  Curved  Line  Drawing"  are  made  in  block 
letters  of  two  different  types,  but  of  straight  lines  only.  See  pp. 
80  and  8 1  for  the  former  and  p.  82  for  the  latter.  The  word 
"Drawing"  is  on  a  lower  line  as  the  entire  inscription  would  be 
too  long.  The  remainder  of  the  legend  except  the  name  is  made 
in  free-hand  lettering."  The  name  is  an  autograph. 

Above  each  figure  the  number  of  the  figure  is  centrally 
placed,  as  Fig.  A,  Fig.  B,  etc.,  in  "  free-hand  lettering."  The 
bottom  line  of  the  lettering  is  J-"  above  the  top  of  the  figures. 


136  MECHANICAL   DRAWING. 

The  scale  is  centrally  placed  below  each  figure,  the  bottom 
line  of  the  lettering  f "  below  the  bottom  of  the  figure.  This  is 
also  "free-hand  lettering." 

The  effect  is  improved  by  drawing  moderately  heavy  black 
lines  just  under  the  lettering. 

The  boundaries  of  all  figures  are  shaded  on  the  right  and 
bottom. 

Border  Line. — After  the  lettering  is  completed,  the  border 
line  is  drawn.  See  "  Border  Line."  The  drawing  is  cleaned  and 
finally  inspected.  It  is  then  cut  from  the  board. 


in 


D 


v_ 


Sca/e, 


'Scale,  Full  Size,  Decimal 


3  cafe,  Full Size. 


STRAIGHT  &  CURVED  LINE 
DRAWING 


(forj  4"1  Class 


Oct.  10  1910. 


SHEET    II. 
WORKING   DRAWINGS. 

SKETCHING;  VIEWS;  CENTER  LINKS;  PROJECTION;  SECTIONS;    HATCH- 
ING;   DIMENSIONS.       (SEE   REMARKS   UNDER   THESE   HEADS.) 

Description  of  Models. — Three  brass  models  are  used  for 
this  sheet.  These  are  cut  across  in  certain  planes  and  the 
parts  are  pinned  together.  They  may  be  separated  into  parts 
in  order  to  study  and  draw  sections.  The  models  are  consid- 
ered to  be  solid  and  are  drawn  accordingly.  The  lines  of 
separation  are  generally  along  center  lines. 

The  dowel  pins  and  holes  are  not  drawn. 

The  different  models  of  each  kind  differ  slightly  in  dimen- 
sions, so  that  care  must  be  taken  to  note  the  marks  on  the 
models  used,  as  it  may  be  necessary  to  again  refer  to  them  after 
the  sketches  are  made.  Models  are  marked  on  each  portion 
with  the  same  characters.  Where  the  portions  are  of  the  same 
shape,  center-punch  marks  are  placed  opposite  each  other  on 
opposite  sides  of  a  plane  of  separation:  as,  — ; — ,  :  :  ,  :  :  :  , 
etc. 

This  conforms  to  engineering  practice. 

GENERAL   DIRECTIONS    FOR   WORK. 

Tack  paper  for  this  sheet. 

The  drawings  of  the  views  are  to  "  Scale,  full  size." 
The  sheet  is  to  be  inked  and  completed,  not  traced. 
Sketch  model  I. 

Inspection  of  sketch. 

Pencil  the  views  of  model  I  on  drawing-paper. 

137 


138  MECHANICAL   DRAWING. 

Inspection. 

Cover  drawing  with  paper. 
Same,  model  II. 
Same,  model  III. 
Pencil  legend. 
Inspection. 
Ink  and  completely  finish  the  views  of  model  I. 

Inspection. 

Cover  drawing  with  paper. 
Same,  model  II. 
Same,  model  II'L 

Ink  legend,  draw  border,  clean  drawing. 
Inspection. 
Cut  drawing  from  board. 

GENERAL    DESCRIPTION    OF    SKETCHING. 

Sketches  of  the  different  views  of  each  model  are  first  made 
in  the  sketch-books.  Note  carefully  that  no  instruments  but 
the  medium  hard  lead-pencil  are  used  in  making  the  sketches. 
Even  the  center  lines  and  the  arcs  must  be  drawn  free-hand. 

Only  the  foot  rule  and  the  calipers  are  used  in  making  the 
measurements. 

Unless  the  model  is  large,  it  is  best  to  make  the  sketches 
of  such  a  size  that  they  will  all  go  on  one  page  or  two  facing 
pages  of  the.  sketch-book.  The  different  views  must  be  pro- 
portioned in  size  to  the  real  sizes  of  the  views  of  the  models. 

As  the  number  of  views  and  sections  required  for  this  sheet 
are  given,  decide  for  each  model  whether  to  make  them  of  a 
size  that  will  fit  on  one  or  two  pages  and  thus  decide  approxi- 
mately how  large  each  view  must  be  sketched  and  the  position 
it  will  occupy  in  the  sketch-book. 

Always  fix  the  positions  of  the  Plan,  Front  Elevation,  and 
Side  Elevation  first  and  draw  them  first.  Later  on,  place  the 
sections  where  most  convenient.  If  the  book  is  large  enough 


FIRST  DRA  WINGS.  139 

to  place  the  sections  so  that  they  may  be  partly  projected  from 
one  of  the  other  views,  it  is  well  to  arrange  the  positions  of  the 
sections  accordingly.  Generally,  however,  sections  are  placed 
in  any  convenient  position  after  the  main  views  are  drawn. 

It  is  generally  best  to  draw  the  Plan  first  and  project  from 
that  for  the  Front  Elevation,  but  it  must  be  decided  upon  in 
each  case. 

First  draw  the  vertical  center  line  for  the  Plan  and  Front 
Elevation.  Then  decide  on  the  position  of  and  draw  horizontal 
center  lines  for  the  Plan  and  for  the  Front  and  Side  Elevations, 
if  the  views  are  symmetrical  about  centers.  Next  draw  a  ver- 
tical center  line  for  the  Side  Elevation.  This  establishes  the 
positions  of  the  central  points  of  the  views,  if  symmetrical.  If 
the  views  are  not  symmetrical,  decide  on  whatever  center  lines 
there  are  and  draw  them. 

After  deciding  on  the  view  to  be  sketched  first,  place  the 
object  or  yourself  in  such  a  position  that  the  face  that  is  to  be 
sketched  of  the  model  is  normal  to  the  line  of  sight.  Draw 
the  principal  boundaries  first,  if  the  figure  is  symmetrical  care- 
fully making  the  corresponding  boundaries  equally  distant  from 
the  center  line.  Draw  all  lines  that  appear  to  view  first  and 
later  put  in  the  hidden  lines  as  broken  lines. 

After  the  first  sketch  is  completed,  draw  next  the  one  that 
seems  most  easily  sketched  and  measured.  Each  correspond- 
ing point  and  line  must  be  projected  vertically  or  horizontally. 

After  the  Plan,  Front  Elevation,  and  Side  Elevation  are 
sketched,  place  all  the  necessary  dimension  extension  lines; 
then  the  arrows ;  then  the  dimension  lines.  Measure  the  model 
and  place  the  dimensions  in  the  spaces  left.  Place  each 
dimension  once  only  on  the  views,  but  choose  a  position  for  it 
that  will  show  it  clearly. 

Mark  where  advisable  on  these  views  in  heavy  broken  lines 
the  positions  of  the  planes  where  the  sections  are  to  be  taken ; 
mark  the  ends  of  these  broken  lines ;  ^4—  —B,  C—  -~A 
etc. 


14°  MECHANICAL   DRA  WING. 

After  the  three  views  are  dimensioned,  separate  the  model 
at  the  plane  where  a  section  is  to  be  made  and  place  the  sec- 
tion normal  to  the  line  of  sight.  Either  portion  may  be  drawn 
as  desired,  but  one  is  generally  more  important  on  account  of 
the  part  of  the  model  beyond  the  section  plane.  Note  that 
part  of  the  figure  is  removed  entirely,  and  the  part  remaining 
only  is  drawn  and  the  surfaces  cut  by  the  plane  hatched. 

Choose  a  position  in  the  sketch-book,  if  there  be  space,  so 
that  as  many  points  as  possible  may  be  projected  from  a  view 
already  drawn ;  if  the  size  of  the  book  and  the  other  sketches 
do  not  allow  of  this,  place  the  section  wherever  convenient  and 
sketch  the  portion  of  the  model  remaining  as  if  it  were  a  new 
model,  making  the  sketch  as  near  the  size  of  the  corresponding 
view  already  drawn  as  possible.  Draw  the  vertical  center  line 
and  any  other  center  lines  first.  As  before,  draw  all  lines  that 
appear  to  the  eye  first  and  later  the  hidden  lines.  Note  that 
all  the  lines  beyond  the  section  plane  must  be  drawn.  When 
completed,  hatch  rapidly,  free-hand,  either  a  portion  or  all  of 
each  surface  cut  by  the  plane,  using  the  proper  Standard  Hatch- 
ing. Hatch  enough  to  clearly  indicate  what  metal  is  used  and 
how  far  the  surfaces  extend. 

Mark  the  section  sketched,  Section  on ,  to  agree 

with  the  letters  placed  on  one  of  the  other  views  to  show  where 
the  section  is  taken. 

Make  sketches  of  all  the  required  sections. 

It  is  seldom,  except  in  very  complicated  drawings,  that 
many  dimensions  are  placed  on  a  section.  It  is  never  done  if 
the  dimensions  may  be  conveniently  placed  on  the  other  views. 

Over  the  sketches  for  this  sheet  only  place  the  names  of  the 
views  sketched  and  draw  projection  lines  for  every  point  or 
surface  projected. 

The  projection  lines  are  short  dashes  and  extend  for  only 
a  distance  of  J"  to  f "  away  from  the  point  or  surface  pro- 
jected and  the  same  distance  back  from  the  position  projected 
to. 


FIRST  DRA  WINGS.  141 

When  all  the  sketches  of  each  model  are  completed,  they 
are  inspected  before  the  drawing  is  begun. 

GENERAL    DIRECTIONS    FOR    DRAWING   SHEET   II. 

Working  line 15"  X  2l" 

Border  line 16"  X  22" 

Cutting  line 18"  X  24" 

The  legend  is  placed  in  the  lower  right-hand  portion,  as 
usual,  and  is  as  follows: 

SHEET  II.      [Block  lettering  of  simple  type.] 
WORKING  DRAWINGS.     [Free-hand  lettering,  large.] 
Sketching;   Views;   Center  lines;   Projection;  Sections;  Hatching; 
Dimensions.     [Free-hand  lettering,   small.] 

Sketched  and  drawn  from  brass  models. 

Scale.  [Free-hand  lettering,  small.] 

Name.  [Autograph.]     Date.  [Free-hand  lettering,  small.]     Class.  [Same.] 

On  this  sheet  only  place  the  names  of  the  views  over  them 
in  free-hand  lettering. 

When  sections  are  made,  place  above  the  views  in  free- 
hand lettering,  Section  on ,  using  the  same  letters  that 

mark  the  section  plane  in  one  of  the  views.  This  applies  to 
all  drawings. 

On  this  sheet  only  draw  projection  lines  for  every  point  pro- 
jected. The  projection  lines  are  not  made  of  dots,  but  of  very 
short  dashes.  They  extend  for  only  a  distance  of  J"  to  f" 
away  from  the  point  projected  and  the  same  distance  back  from 
the  position  projected  to. 

Make  the  pencil-lines  full  and  broken  lines  as  required. 

Do  no  hatching  in  pencil. 

Draw  no  projection  lines  in  pencil. 

Place  no  dimensions  in  pencil. 

Ink-work. — Carry  out  the  established  method  of  drawing 
all  vertical  lines  first,  full  and  broken,  and  then  sweep  down 
the  board  with  the  T  square  for  all  horizontal  lines  wherever 
found.  All  lines  of  the  figures  are  standard. 


I42  MECHANICAL   DRAWING. 

When  the  shade  lines  are  drawn,  set  the  pen  to  proper 
width  and  never  change  the  setting  while  drawing  the  shade 
lines. 

Carry  out  the  "  Plan  of  Procedure  "  for  inking. 
-  Note  carefully  which  lines  are   to   be  drawn    broken  and 
which  surfaces  hatched.      The  sketches  should  be  so  complete 
in  these  details  that  they  may  be  followed  absolutely  in  inking 
the  drawing. 

POSITIONS    OF   THE    VIEWS    ON    THE    SHEET. 

A  distance  of  -J-"  separates  horizontally  all  views  of  the 
same  model.  The  vertical  distances  between  the  views  are 
given  for  each  model. 

Place  the  views  of  model  I  as  follows: 
Section  on  CD. 
Plan. 

Front  Elevation.      Side  Elevation. 
Section  on  AB.      Section  on  EF. 

The  views  to  the  left  touch  the  left  hand,  top,  and  bottom 
working  lines.  The  vertical  distances  between  the  views  are 
equal. 

In  the  space  to  the  right  of  ' '  Section  on  CD  ' '  is  placed : 

MODEL  I. 

GUIDE-BLOCK. 

Place  the  views  of  model  II  as  follows: 

Plan 

Side  Elevation,  half  section  on  CD.       Front  Elevation. 

Section  on  AB. 

The  vertical  center  line  of  the  Plan  is  on  the  vertical  center 
line  of  the  sheet.  The  top  of  the  Plan  touches  the  top  working 
edge.  A  vertical  distance  of  i£"  separates  the  views  in  the 
same  vertical  line. 

In  the  space  below  "  Section  on  AB  "  and  centrally  under 
it  is  placed : 


FIRST  DRA  WINGS.  143 

MODEL  II. 

BOTTOM  JOURNAL   BRASS. 

Place  the  views  of  model  III  as  follows: 

Plan. 

Front  Elevation.      Side  Elevation,  half  section  on  AB. 

Section  on  CD. 

The  "  Side  Elevation,  half  section  "  touches  the  right-hand 
working  line. 

A  vertical  distance  of  J"  separates  the  views  in  the  same 
vertical  line. 

In  the  space  to  the  right  of  the  Plan  is  placed: 

MODEL  III. 

CROSS-HEAD. 


MODEL  I. 

Make  a  working  drawing  of  the  model  of  a  guide-block. 

Three  views,  Plan;  Front  Elevation ;  Side  Elevation:  and 
sections  through  the  horizontal  center  line  of  the  Plan;  the 
vertical  center  line  of  the  Front  Elevation ;  and  through  a  hori- 
zontal plane  about  \"  below  the  top  of  the  Front  Elevation. 

The  figure  represents  a  block  of  cast  iron  which  is  bolted 
to  the  framing  of  an  engine  by  bolts  passing  through  holes  (not 
shown)  extending  vertically  through  at  the  points  marked  for 
the  centers  of  the  curves  of  the  corners.  The  rectangular 
depression  acts  as  a  guide  to  a  rectangular  rod  moving  back 
and  forth  longitudinally. 

The  moving  rod  is  horizontal,  therefore  the  Plan  will  be 
the  view  looking  down  on  the  model  placed  so  that  the 
depressed  portion  is  seen  from  above. 

Sketching. — Draw  the  vertical  center  line  for  the  Plan  and 
Front  Elevation ;  horizontal  center  line  for  the  Plan ;  horizon- 
tal center  line  for  the  Front  and  Side  Elevations ;  and  vertical 
center  line  for  the  Side  Elevation. 

Sketch  the  Plan.     Project  downwards  from  each  vertical 


144 


MECHANICAL   DRAWING. 


line  of  the  Plan  a  series  of  short  dashes.  These  define  the 
limits  of  the  horizontal  lines  in  the  Front  Elevation.  Sketch 
the  Front  Elevation,  using  these  projection  lines  for  limits  for 
the  horizontal  lines.  The  lengths  of  the  vertical  lines  are 
decided  by  eye,  noting  that  the  boundaries  of  the  view  are 
equally  distant  from  the  horizontal  center  line.  Note  the 


P/an 


a 


FIRST  DRAWINGS. 


145 


hidden  lines  showing  that  the  depressions  on  the  vertical  side 
boundaries  of  the  Plan  appear  as  vertical  lines  in  the  Front 
Elevation.  These  are  projected  from  the  Plan,  or  the  surface 
a  projects  to  a'a". 

Draw  projection  lines  horizontally  from  all  horizontal  lines 
of  the  Front  Elevation.  These  define  the  limits  of  the  vertical 
lines  of  the  Side  Elevation. 

Sketch  the  Side  Elevation,  using  the  projection  lines  from 
the  Front  Elevation  as  limits  for  the  vertical  lines.  The 
lengths  of  the  horizontal  lines  are  determined  by  eye,  noting 
that  the  boundaries  of  the  views  are  equally  distant  from  the 
vertical  center  line,  and  that  the  horizontal  lengths  of  this  view 
should  agree  with  the  vertical  heights  of  the  corresponding 
lengths  in  the  Plan.  Note  that  the  bottom  of  the  depression 
in  the  Front  Elevation  becomes  a  hidden  line  in  the  Side 
Elevation,  the  line  extending  across  the  view. 

Dimensions. — Place  arrows,  as  shown,  for  measurements 
and  draw  dimension  extension  and  dimension  lines.  The  radii 
of  the  arcs  in  the  Plan  must  be  given  and  the  positions  of  the 
centers.  Note  that  no  dimensions  are  required  for  the  Side 
Elevation,  dimensions  in  the  vertical  direction  being  given  in 
the  Front  Elevation  and  in  the  horizontal  direction  in  the  Plan. 

The  sketches  are  now  complete  as  far  as  the  main  views 
are  concerned. 


146 


MECHANICAL   DRAWING. 


Sections. — Sections  are  required  on  planes  ABy  CD,  and 
EF.  Mark  these  planes  on  the  proper  views  with  heavy 
broken  lines  and  letter  them,  as  shown. 

As  stated,  place  these  views  in  the  sketch-books  to  best 
advantage. 

Section  on  AB. — Divide  the  model  on  the  line  AB  and 
sketch  one  portion,  looking  towards  the  surface  cut  by  the 


plane.  The  position  with  reference  to  the  model  is  the  same 
as  when  the  Front  Elevation  was  sketched. 

Sketch  the  model  as  it  appears. 

Note  that  the  outer  boundary  is  the  same  as  that  of  the 
Front  Elevation.  Part  of  the  view  could,  then,  be  readily 
projected  from  the  Front  Elevation. 

Hatch  the  surface  cut  by  the  plane.  Use  the  Standard 
Hatching  for  cast  iron.  Mark  the  sketch,  "  Section  on  AB." 

Section  on  CD. — Join  the  portions  of  the  model  and  divide 
it  on  the  plane  CD.  Sketch  the  larger  portion,  looking 
towards  the  surface  cut  by  the  plane.  The  position  with  refer- 
ence to  the  model  is  the  same  as  when  the  Plan  was  drawn. 

Sketch  the  model  as  it  appears.  It  is  exactly  the  Plan 
repeated,  except  that  the  side  portions  are  hatched  where  cut 
by  the  plane.  Part  of  the  sketch  could  be  readily  projected  if 
placed  at  the  top  or  side  of  the  Plan. 


FIRST  DRA  WINGS. 


Section  on  EF. — Join  the  portions  of  the  model  and  divide 
again  on  the  plane  EF. 

Sketch  one  portion,  looking  towards  the  surface  cut  by  the 


plane.      The  position  is  the  same  as  when  the  Side  Elevation 
was  drawn. 

Sketch  the  model  as  it  appears  and  hatch  the  surface  cut 
by  the  plane. 


148  MECHANICAL   DRAWING. 

Note  that  the  lines  showing  the  intersections  of  the  curved 
corners  with  the  side  boundaries  in  the  middle  of  the  height 
become  vertical  broken  lines. 

Part  of  the  sketch  could  be  projected  from  the  Side  Eleva- 
tion and  the  rest  from  the  Front  Elevation. 

Mark  the  sketch,  "  Section  on  EF." 

Below  the  sketches  and  in  the  lower  right-hand  corner  of 
the  page,  write: 

Model  I.      Guide-block. 

DIRECTIONS   FOR   DRAWING   MODEL   I. 

Pencil-work. — After  centering  the  paper  and  drawing  the 
three  dimension  lines  of  the  sheet,  note  that  the  views  to  the 
left  of  model  I  touch  the  left-hand  and  the  top  and  bottom 
working  lines. 

From  the  sketches,  decide  on  the  position  of  the  vertical 
center  line  of  the  left-hand  views  and  draw  it  vertically  the 
whole  length  of  the  working  line. 

From  the  sketches,  decide  on  the  total  vertical  distance 
remaining  for  spaces  between  the  views  and  divide  this  distance 
equally  for  the  spaces. 

Draw  the  extreme  horizontal  bounding  lines  of  the  views 
and  their  horizontal  center  lines.  Check  to  see  that  there  is 
the  same  distance  between  the  views. 

Plan. — Draw  the  Plan  first.  Measure  when  possible  from 
the  center  lines  half  the  dimensions  on  either  side.  Make  as 
few  measurements  as  possible.  Measure  once  and  project  up 
and  down  or  sideways  for  corresponding  points.  Fix  the 
center  of  one  of  the  bolt-holes  and  project  in  directions  at  right 
angles.  Fix  the  center  of  the  diagonally  opposite  one  and 
again  project  in  directions  at  right  angles.  This  establishes 
the  four  centers. 

Front  Elevation. — Project  vertically  downward  from  the 
Plan  the  lines  of  the  vertical  surfaces  and  draw  them  across  the 
view  of  the  Front  Elevation.  Only  one  measurement  is  made 


FIRST  DRAWINGS.  149 

— that  for  the  depth  of  the  depression  in  the  model.  Draw  the 
hidden  lines,  projecting  properly. 

Carefully  mark  on  the  Plan  and  Front  Elevation  the  posi- 
tions of  the  planes  where  sections  are  to  be  taken. 

Side  Elevation. — Project  horizontally  from  the  Front  Eleva- 
tion, noting  that  the  bottom  of  the  depression  in  the  model 
becomes  a  broken  line.  The  horizontal  distances  need  not  be 
measured ;  they  may  be  taken  with  the  dividers  from  the  ver- 
tical distances  on  the  Plan. 

Section  on  AB. — Project  downward  from  the  Front  Eleva- 
tion. The  vertical  dimensions  may  be  taken  from  the  Front 
Elevation  by  dividers. 

Section  on  CD. — Project  upwards  from  the  Plan  and  make 
the  view  the  same  as  the  Plan,  as  in  the  sketch. 

Section  on  EF. — Project  horizontally  from  "  Section  on 
AB"  and  downwards  from  the  Side  Elevation.  The  view  is 
entirely  finished  from  these  projections. 

Note  the  part  to  be  hatched. 

Ink  according  to  directions. 

MODEL  II. 

Make  a  working  drawing  of  a  model  of  a  Bottom  Journal 
Brass.  Metal :  composition.  Three  views :  Plan ;  Front  Eleva- 
tion; Side  Elevation,  half  in  section;  and  a  section  through 
the  horizontal  center  line  of  the  Plan.  Scale,  full  size. 

The  model  represents  the  lower  half  of  a  pair  of  '  *  Brasses  ' ' 
in  which  a  shaft  revolves.  It  is  made  "flat  sided"  on  the 
under  side  to  prevent  its  turning  in  the  framing  in  which  it 
rests. 

As  it  is  the  lower  "brass,"  the  Plan  is  the  view  looking 
into  the  concave  surface. 

In  this  case,  in  order  to  fit  better  on  the  drawing-paper, 
the  Side  Elevation  is  taken  to  the  left. 

Sketching. — It  will  be  found  best  to  sketch  the  Front 
Elevation  first,  as  one  measurement  only  is  required  for  the 


150  MECHANICAL  DRAWING. 

diameters  of  the  half  circles  shown  on  the  Front  Elevation,  and 
the  radii  used  will  define  both  ends  of  the  diameters,  which 
may  be  projected  vertically  to  the  Plan.  The  basis  of  work  in 
this  view  is,  then,  the  top  line  of  the  brass. 

Note  also  that  the  shape  of  the  "  flat-sided  "  portion  of  the 
bottom  of  the  "brass  "  is  drawn  in  the  Front  Elevation  and 
the  edges  projected  to  the  Plan. 

There  are  many  more  hidden  lines  than  in  the  views  of 
model  I;  all  must  be  carefully  drawn. 

Draw  the  vertical  center  line  for  the  Plan  and  Front  Eleva- 
tion. Leave  space  above  for  the  Plan  and  sketch  the  Front 
Elevation.  Project  upwards  and  sketch  the  Plan. 

Note  that  the  flanges  of  the  brass  are  semi-circles  except 
for  short  vertical  portions,  but  their  center  is  not  coincident 
with  the  center  of  the  circles  of  the  bearing.  The  position  of 
this  center  is  dimensioned  on  the  sketch. 

Carefully  mark  the  positions  of  the  planes  where  sections 
are  to  be  taken. 

The  Side  Elevation  is  projected  to  the  right  or  left  of  the 
Front  Elevation.  Draw  a  vertical  center  line  for  this  view  at 
the  proper  distance  away  from  the  Front  Elevation.  Sketch 
half  of  this  view  only — the  portion  to  the  right  or  left  of  the 
vertical  center  line. 


FIRST   DRAWINGS. 


To  finish  the  Side  Elevation,  half  in  section,  separate  the 
model  on  the  plane  CD  and  hold  the  half  that  is  used  in  the 
same  position  as  when  sketching  the  Side  Elevation.  Sketch 
half  of  the  half  model,  placing  proper  Standard  Hatching  on 
the  surface  cut  by  the  plane. 

Note  that  the  outline  is  the  same  as  for  the  rest  of  the  view, 
the  difference  being  in  the  lines  seen  and  hidden, 

The  vertical  line  separating  the  elevation  from  the  section 


r       • 

... 

1 

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152 


MECHANICAL   DRAWING. 


is  a  full  line.     The  center  line  continues  beyond  above  and 

below. 

Mark  the  view,  Side  Elevation.      "  Half  section  on  CD." 
Dimensions.  —  Place  arrows,  lines,  etc.,  for  measurements, 

as  shown.      Note  that  all  the  measurements  are  on  the  Plan 

and  Front  Elevation.      All  arcs  are  dimensioned  by  diameters 

where  possible. 

Section  on  AB.  —  Unite  the  parts  of  the  model  and  separate 

again  on  the  plane  AB.     Place  the  half  model  so  that  the  sur- 


face  cut  by  the  plane  is  at  right  angles  to  the  line  of  sight  and 
sketch  it. 

Note  that  the  model  is  now  in  the  same  position  as  when 
the  Front  Elevation  was  drawn,  and  that  the  boundary  is  the 
same.  Hence  this  view  might  be  largely  projected  from  the 
Front  Elevation. 

Hatch  the  surface  cut  by  the  plane.  Note  carefully  the 
hidden  lines. 

This  sketch  is  placed  so  it  may  be  projected,  if  possible. 

Mark  the  sketch,  "Section  on  AB." 

Mark  the  sketches,  "  Model  II.     Bottom  Journal  Brass." 


FIRST  DRAWINGS.  1 53 

DIRECTIONS    FOR    DRAWING    MODEL   II. 

Draw  the  vertical  center  line  for  the  Plan,  Front  Elevation, 
and  Section  on  AB,  and  the  horizontal  center  line  for  the  Plan. 

Draw  the  horizontal  boundary  lines  for  the  Plan  and  the 
top  line  of  the  Front  Elevation.  On  this  last  line  measure  from 
the  vertical  center  line,  the  radii  of  the  arcs  having  this  point 
for  a  center,  and  draw  the  arcs;  the  distances  for  the  vertical 
parts  of  the  ' '  flat-sided  ' '  portions  of  the  base  and  draw  vertical 
lines;  and  the  half  extreme  horizontal  dimensions  of  the 
"  brass  "  and  draw  vertical  lines.  Measure  from  the  top  line 
down  the  vertical  center  line  for  the  position  of  the  center  of 
the  lower  bounding  arc  and  with  the  proper  radius  draw  the 
arc.  This  arc  should  join  tangentially  the  vertical  lines  for  the 
outer  vertical  boundaries.  Measure  downward  from  the  same 
point  for  the  position  of  the  bottom  of  the  '  *  flat-sided  ' '  portion 
of  the  base  of  the  '  *  brass  ' '  and  for  the  depth  of  the  vertical 
•flat  portion  on  the  two  sides.  Draw  an  indefinite  line  for  the 
bottom  flat  and  measure  along  it  the  half  widths.  This  defines 
the  bottom  edges.  Project  across  from  the  measurements 
taken  for  the  ends  of  the  vertical  ' '  flat-sided  ' '  portions.  Con- 
nect the  two  sets  of  points  last  found  on  the  two  sides.  The 
lines  connecting  the  portions  of  the  under  part  are  thus  deter- 
mined. 

Project  upwards  for  the  Plan.  All  the  necessary  measure- 
ments are  made  on  the  vertical  center  line,  and  the  horizontal 
lines  are  drawn  in  the  proper  places  from  these  measurements. 
In  this  case,  all  the  lines  cross  the  figure  to  their  respective 
boundaries,  which  are  projected  upwards  from  the  Front  Eleva- 
tion. The  radii  of  the  curves  at  the  corners  are  not  important, 
but  the  approximate  radii  found  for  the  sketches  are  used. 
The  radii  are  about  j-". 

Draw  the  vertical  center  line  for  the  Side  Elevation,  half  in 
section. 

Project  to  the  left  from  the  Front  Elevation  for  the  horizon- 


*54  MECHANICAL   DRAWING. 

tal  lines.  The  horizontal  dimensions  are  obtained  from  the 
vertical  heights  of  the  Plan.  Measure  always  from  the  vertical 
center  line.  Note  that  the  lines  are  the  same  for  both  parts  of 
the  view  in  the  pencil-work,  some  full,  some  broken. 

Section  on  AB. — As  this  is  simply  a  copy  of  the  Front 
Elevation  with  a  variation  in  the  lines  made  full  or  broken, 
project  down  from  the  Front  Elevation  and  take  the  vertical 
measurements  from  it  with  the  dividers.  Lay  these  measure- 
ments off  on  the  vertical  center  line  as  usual  and  project  across. 

Ink  according  to  directions. 

MODEL    III. 

Make  a  working  drawing  of  a  model  of  a  cast-steel  Cross- 
head  for  a  small  horizontal  engine.  Three  views :  Plan ;  Front 
Elevation;  Side  Elevation,  half  in  section;  and  a  section 
through  the  horizontal  center  line  of  the  Plan.  Scale,  full  size. 

The  figure  represents  the  sliding-block  of  metal  that  con- 
nects the  reciprocating  or  "  back-and-forth  "  motion  of  the 
piston  and  piston-rod  in  the  cylinder  with  the  rotary  motion  of 
the  crank  and  the  shaft.  As  the  engine  is  horizontal,  the 
broad,  flat  portion  is  below  and  furnishes  a  large  surface  for 
support  as  the  Cross-head  moves  back  and  forth  on  the  guide. 
Therefore,  the  Plan  view  is  the  one  where  the  flat  portion  is 
downwards. 

The  two  cylindrical  portions  show  where  the  forked  "con- 
necting-rod," that  connects  the  cross-head  and  the  crank-pin, 
grasps  the  cross-head.  These  are  called  journals.  Note  care- 
fully the  fillets  where  the  journals  join  the  main  casting.  The 
piston-rod  is  secured  through  the  middle  of  the  square-faced 
portion  between  the  cylindrical  pins.  The  hole  for  this  is  not 
shown.  The  projection  on  the  side  of  the  cross-head  is  for  the 
purpose  of  securing  there  a  horizontal  pump-rod  which  moves 
with  the  cross-head.  The  center  of  the  hole  for  the  rod  is  in- 
dicated. 

Sketching. — In  this  case  the  figure  is  generally  symmetrical 
in  the  Plan  view,  but  not  so  much  so  in  the  other  views ;  so  the 


FIRST    DRAWINGS. 


155 


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156  MECHANICAL   DRAWING. 

vertical  center  line  for  the  Plan  and  Front  Elevation  is  drawn 
and  the  horizontal  center  line  for  the  Plan,  but  no  horizontal 
center  line  for  the  Front  Elevation  and  Side  Elevation.  The 
vertical  center  line  for  the  Side  Elevation  may  now  be  drawn, 
but  it  is  better  to  wait  until  the  Front  Elevation  is  completed. 
Also,  it  may  be  readily  seen  that  it  is  better  to  sketch  the  Front 
Elevation  first,  as  it  gives  a  better  view  and  a  better  under- 
standing of  the  model. 

Leave  room  for  the  Plan  above.  Draw  a  center  line  for  the 
two  cylindrical  portions,  or  journals,  and  extend  this  for  the 
Side  Elevation.  Sketch  the  Front  Elevation  and  project  for 
the  Side  Elevation  and  Plan.  Mark  the  views  properly.  Note 
carefully  what  lines  of  the  Plan  are  concealed  by  the  projecting 
portions  above. 

For  the  half-section  on  AB  separate  the  model  on  that 
plane  and  place  it  normal  to  the  line  of  sight  and  sketch  it. 
The  outline  corresponds  with  that  of  the  Side  Elevation,  as  the 
part  remaining  beyond  the  section  is  a  fac-simile  of  the  part 
already  sketched. 

Note  that  the  circle  seen  by  looking  at  the  end  of  the 
journal  becomes  a  broken  line  in  the  section,  as  the  nearer 
cylinder  is  removed  and  the  farther  one  is  hidden.  Note  also 
that  the  lines  defining  the  outline  of  the  portion  for  securing  the 
pump-rod  are  now  gone,  as  all  this  portion  is  removed. 

Mark  the  sketch,   "Side  Elevation,  half-section  on  AB." 

Dimensions. — Place  arrows,  etc.,  as  shown.  The  dimen- 
sions are  again  placed  on  the  Plan  and  Front  Elevation  only. 
The  approximate  shapes  of  the  arcs  defining  the  outlines  are 
determined  after  the  drawing  is  made  on  the  drawing-board, 
as  they  are  simply  clean  arcs  joining  the  determined  points. 
The  positions  of  the  beginning  and  ending  of  these  arcs  must 
be  accurately  determined  and  noted  on  the  sketches.  The 
center  of  the  pump-rod  is  the  center  of  the  arc  around  the 
metal  at  that  place  and  is  accurately  shown,  as  well  as  the 
radius  of  the  curve. 


FIRST  DRA  WINGS. 


157 


Section  on  CD. — Separate  the  model  on  the  plane. 
Place  the  sketch   as  advisable  in  the  sketch-book,  noting 
that  portions  of  it  may  be  projected  from  any  of  the  other  views. 

Secfion  on  CD 


It  is  seen  that  the  outline  exactly  corresponds  with  that  of  the 
Front  Elevation  and  that  the  entire  surface  is  hatched.  Care- 
fully draw  all  broken  lines  representing  hidden  lines  beyond 
the  section. 

Mark  the  sketch,  "  Section  on  CD." 

Mark  the  set  of  sketches, 

MODEL  III. 

C  ROSS-HEAD. 
DIRECTIONS    FOR    DRAWING    MODEL    III. 

Lay  off  along  the  top  working  line  from  the  upper  right- 
hand  corner  the  distance  of  the  half  width  of  the  Side  Elevation 
and  draw  a  vertical  center  line  of  indefinite  length  for  the 
center  line  of  the  Side  Elevation. 

From  the  sketches,   determine  the    distance  between  this 


158  MECHANICAL   DRAWING. 

center  line  and  the  one  through  the  Plan,  Front  Elevation,  and 
Section  on  CD,  allowing  the  proper  distance  between  the  views, 
and  draw  the  new  center  line.  Lay  off  downward  on  this 
center  line  from  the  top  working  line  the  half  height  of  the  Plan 
view  and  draw  the  horizontal  center  line  for  the  Plan.  Draw 
the  boundaries  of  the  base  in  the  Plan. 

From  the  lower  boundary  of  the  Plan  lay  off  the  proper 
amount  for  the  vertical  distance  between  the  views  and  draw 
the  top  line  of  the  Front  Elevation.  Next  draw  the  center 
line  for  the  journals  and  continue  to  draw  the  figure  from  the 
dimensions  of  the  sketches,  measuring  always  along  center  lines 
when  possible. 

After  completing  the  Front  Elevation,  project  for  the  hori- 
zontal lines  of  the  Side  Elevation  and  the  vertical  lines  of  the 
Plan.  Either  Plan  or  Side  Elevation  maybe  finished  first;  but 
it  is  easier  to  draw  the  Side  Elevation  using  the  dimensions 
given  on  the  Plan  sketch,  and  then  take  these  dimensions  with 
the  dividers  from  the  Side  Elevation  and  use  them  in  drawing 
the  Plan. 

The  curved  lines  for  the  boundaries  of  the  curved  surfaces 
extending  from  the  upper  to  the  lower  parts  of  the  Front  and 
Side  Elevations  are  not  necessarily  arcs  of  circles,  but  are 
generally  drawn  as  such,  as  the  pattern-maker  does  not  require 
accurate  curves  and  will  fashion  them  as  required  when  he 
makes  the  pattern  for  casting.  The  arcs  are  drawn  tangent  at 
points  a  and  c  (see  sketch)  and  of  radii  such  that  the  lower  por- 
tions of  the  arcs  reach  the  points  b  and  d.  A  third  point  on  the 
curve  is  found  by  laying  a  straight  edge  (side  of  a  triangle)  from 
a  to  b  and  c  to  d.  The  edge  is  a  chord  and  the  distance  to  the 
arc  at  the  middle  point  may  be  measured  and  the  point  thus 
plotted.  These  radii  and  the  positions  of  the  centers  on  the 
horizontal  line  through  aa  and  cc  are  found  by  trial.  The  direc- 
tion of  curvature  of  these  edges,  as  they  appear  in  the  plan,  must 
be  worked  out  as  a  problem  in  the  intersection  of  two  cylinders. 
The  best  solution  is  by  passing  planes  parallel  to  H.  The  two 


FIRST    DRAWINGS.  159 

end  points  of  this  curve  are  already  determined  and  a  few  inter- 
mediate ones  are  plotted  and  a  curve  drawn  in  with  the  irregular 
curves.  The  same  portion  of  the  curve  is  used  in  all  four  places, 
reversing  the  curve  for  two  of  them. 

The  curve  in  the  Front  Elevation  defining  the  boundary  of 
the  surface  extending  down  to  the  side  extension  for  the  pump- 
rod  is  drawn  as  an  arc  of  a  circle  with  its  center  on  the  line  aa 
and  a  radius  and  position  of  center  (found  by  trial)  to  cause  the 
arc  to  join  at  a  tangent  the  arc  drawn  with  the  center  of  the  hole 
for  the  pump-rod  as  a  center. 

Half-section  on  AB.- — This  corresponds  with  portions  of  the 
Side  Elevation,  as  shown  in  the  sketch,  and  is  drawn  at  the 
same  time  as  the  Side  Elevation. 

Section  on  CD.  — This  is  a  reproduction  of  the  outlines  of 
the  Frpnt  Elevation,  so  that  vertical  projections  define  all  hori- 
zontal lengths  and  the  vertical  distances  are  taken  from  the 
Front  Elevation  with  the  dividers. 

Carefully  draw  the  horizontal  center  line  first. 

Ink  according  to  directions. 


Legend. — In  inking  the  legend,  use  as  little  time  as  possible. 
Do  not  make  the  block  letters  solid  unless  they  are  sufficiently 
narrow  so  that  a  stroke  of  the  R.  L.  pen  will  suffice. 

Make  the  border  simple  and  make  the  right-hand  and 
bottom  lines  heavier  than  the  others.  The  widths  of  the  parts 
of  the  border  line  should  be  in  accord  with  the  rest  of  the 
drawing. 

When  cleaned  and  inspected,  cut  the  drawing  from  the 
board. 


160 


MECHANICAL    DRAWING. 


STANDARD    DIMENSIONS    OF    BOLTS    AND    NUTS    FOR    THE 
UNITED    STATES    NAVY. 


Diameter. 

Area. 

Threads. 

Long  Diameter. 

Short  D. 

Depth. 

Col.  i. 

Column  2. 

Column  3. 

Column  4. 

Column  5. 

Column  6. 

Column  7. 

Column  8. 

Col.  9. 

Nom. 

Eff. 

Eff. 

No. 

Hex. 

Sq. 

w. 

Head. 

Nut. 

i 

.185 

.026 

20 

A 

If 

j 

, 

j 

A 

.240 
.294 

•  045 
.067 

18 
16 

ff 

i 

F 

* 

•345 
.400 

•093 
-125 

14 
13 

i 

1 

P 

i 

T9* 

-454 

.162 

12 

i* 

If 

!i 

|i 

59ff 

f 

-507 
.620 

•731 

.202 
.302 
.419 

II 
10 

9 

iS 

If 

1 

iA 

ff 

s 

ir 

I 

•837 

.550 

8 

if 

2l5<f 

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61 

FIRST  DRAWINGS. 


161 


STANDARD   HATCHING. 


EARTH. 


CEMENT. 


ALUMINUM, 


1 62  MECHANICAL    DRAWING. 

LINES  TO  BE  USED  ON  DRAWINGS. 

STANDARD    OF  BUREAUS    OF    NAVY    DEPARTMENT. 

All  lines  on  drawings  must  be  black. 

The  standard  lines,  full  or  broken,  used  for  visible  or  con- 
cealed outlines  of  object  are  made  heavier  than  center,  dimen- 
sion, hatching,  or  construction  lines. 

Standard  Lines. 


Center  Lines. 


Dimension  Lines. 


Hatching  Lines. 


Construction  Lines. 


Lines  Indicating  Path  of  Sections. 

Dividing  Lines  of  Partial  Sections  are  made  Free  Hand. 

Section   lines   and   sections   when   not   cutting   through   the- 
centers  of  objects  must  be  indicated  by  letters. 

Shade   lines   are   permitted   in   general   arrangements   only. 

Shade  Line. 


INDEX. 


Arrows,  60 

Beam-compasses,  29 
Block  letters,  78  to  82 
Blue-printing,  97 
Bolts  and  nuts,  70 

standard,  160 
Border  line,  75 
Bow  spacers,  22,  118 
Bow  pencil,  22,  122,  123 
Bow  pen,  22,  122,  123 
Breaks,  56 
Brushes,  29 

Calipers,  30 
Center  Lines,  i,  41 
Centers,  horn,  28 
Compass,  beam,  22,  29 
Compasses,  19,  121,  122 

test,  20 

use,  20 

Cone,  line  shade,  88 
Curves,  irregular,  25 
Cutting  line,  75 
Cylinder,  line  shade,  85 

1  Dimension  extension  lines,  57 
Dimension  lines,  57 
Dimensions,  61 

figures,  6 1 

figures,  decimal,  61 

over  all,  59 
Dividers,  24 

use,  24  . 

Dividing  lines  into  parts,  119 
Drawing-board,  i 

Ellipses,  131 
Erasers,  27 

rubber,  27 

metal,  27 

Erasing  shields,  28 
Extension-bar,  21 

File,  4 

Fillets,  47,  124 


First  drawings,  106 
Flat  tint,  92 

General  arrangement,  34 
General  remarks,  104 
General  view,  Sheet  I,  106,  136 

Hatching,  51,  119 

standard,  161 
Horizontal  lines,  i,  7 
Horn  centers,  28 

Ink,  black,  China,  5 
bottled,  5 
red,  5 

Irregular  curves,  24,  131 
Isinglass,  29 

Jam-nuts,  74 

Leads,  2 

Lead,  sharpening,  3 
Lead- wire,  31 
Legend,  76,  135,  159 
Lettering,  76 

free-hand,  83,  84 
Letters,  block,  28,  79  to  82 
Light,  2 
Lines,  2,  3,  40 

border,  75 
center,  41 
cutting,  75 
dimension,  58 

extension,  58 
shade,  43,  134 

bolt-heads,  49 
sections,  shafts,  etc.,  49 
working,  75 
Line-shading,  84 

cone,  88 
cylinder,  85 

hollow,  88 
sphere,  90 


Marking  dimensions,  5 


163 


164 


INDEX. 


Models,  137 
Model      I,  143 
II,  149 
HI,  154 

Nuts,  70 

jam,  74 

Pads,  for  sharpening  leads,  5 
Paper-cutters,  31 
Paper,  stretching,  32 
Parallel  lines,  to  draw,  8 
Pen,  right-line,  13 
Pencils  and  pencilling,  2 

Artist,  3 

points,  3 

sharpening,  3 

compasses,  3 
Pencil,  use  of,  5 
Pencilling  drawings,  102 
Plan  of  procedure  in  making  a  draw- 
ing, TO  I 
Plan  of  procedure  in  inking  a  drawing, 

103 

Pricker,  5,  29 
Profile  drawings,  34 
Projections,  38 
Protractors,  26,  127 

Right-line  pen,  13 

clean,  use,  etc.,  13-18 
Rule,  foot,  30 

Scales,  10  to  12,  76,  83 
Screw-threads,  62 
Secure  paper  on  board,  2 

tracing-cloth  on  board,  2 
Sections,  50, 118,  146,  147,  150, 151,  152, 

J55»  157 

Shade  lines,  43  to  49,  134 
Sheet    I,  107 

n,  137 


Shields,  erasing,  28 

Sketches,  98,  138,  143,  149,  154 

Spacers,  bow,  22 

Sphere,  line  shade,  90 

Splines,  31 

Standard  bolts  and  nuts,  160 

hatching,  161 
Stippling,  96 

Tails,  74 
Thumb-tacks,  2 
Threads,  double,  etc.,  68 
screw,  62 
square,  67 
Tint,  flat,  92 
Tinting,  91  to  95 

cone,  94,  95 
cylinder,  94 
sphere,  95 
Tracings,  35,  96 
Trams,  29 
Triangles,  8 

test,  9 

45°,  112,  113,  115,  !i6, 
60°,  114,  n6,  117 
Triangular  scale,  10 

use,  13 
guard,  13 
Truing  up,  i 
T  square,  6 


Vertical  lines,  i,  7 
Views,  36 

Weights,  7 

Wire,  lead,  31 

Working  drawings,  35,  137 

business  method,  35 
Working-edge,  i 
Working  line,  75 


V 


J. 


THIS  BOOK  IS  DUE  ON  THE  LAST  DATE 
STAMPED  BELOW 

AN  INITIAL  FINE  OF  25  CENTS 

WILL  BE  ASSESSED  FOR  FAILURE  TO  RETURN 
THIS  BOOK  ON  THE  DATE  DUE.  THE  PENALTY 
WILL  INCREASE  TO  SO  CENTS  ON  THE  FOURTH 
DAY  AND  TO  $!.OO  ON  VFttE  SEVENTH  DAY 
OVERDUE. 


ON  VFttE 
'Jfcl^ 


OCT  24  1933 


SEP  231947 


SEP  13 


LD  21-100m-7,'33 


